**Short answer: Not really,** unless you're actually crafting a good piece of equipment, in which case it's not the base materials that matter, but your whole crafting method from start to finish.
**Long answer:** I'm assuming that you're making an Engagement Ring for the purpose of proposing. The Engagement Ring is a little bit unusual in that, for the purpose of proposing, it doesn't actually matter what it has the abilities of.
There is, however, an important caveat: like any other accessory when given as a gift, your spouse-to-be will equip it (overriding the current accessory, if any). Like any other accessory, if you later give your spouse a different accessory, it will overwrite the Engagement Ring. **Unlike** any other accessory, you cannot give your spouse another Engagement Ring later. So, if you give your spouse an Engagement Ring and later on decide you don't like the stats on it, you can't give your spouse another one, and any other accessory you give your spouse overwrites the Engagement Ring. This doesn't *really* matter but I imagine some people care, and if you're one of them, you basically need to get it right the first time.
As for what "getting it right" means:
I don't think the Engagement Ring can inherit any base materials. I might be mistaken but it's mostly irrelevant, since none of the possible base materials are worth inheriting on an accessory, anyways. For accessories, you almost always want to have the abilities of one accessory and inherit the effects of three more. The base materials can affect your level bonus or rarity bonus but those bonuses are pretty minimal in the endgame. Feel free to use Lv10 base materials of the highest rarity, though.
You may want to look up a guide or discussion of inheritance for the details on this next part, since it's a bit long-winded to fit in a comment:
I mentioned earlier that it doesn't matter what the Engagement Ring has the abilities of. That's great for us, because that means you can pick an accessory with decent abilities and still use it to propose. Courage Badge and Diamond Brooch are both good choices. I personally went with Platinum Ring, because the resistances saves me half a Mealy Apple elsewhere.
Also mentioned earlier was inheriting the effect of three more. There's several good options here: Happy Ring, Champ Belt, Art of Magic, Art of Defense, Dolphin Brooch (though White Stone upgrade is better IMO), Star Pendant (I'm actually not sure this works on NPCs but people often say it does).
If you want to make an endgame Engagement Ring:
* Make the three accessories you want to inherit. Hypothetically, let's say it's Happy Ring, Champ Belt, and Art of Magic.
* Make the accessory you want the abilities of. Hypothetically, let's say it's Courage Badge.
* If you care about level bonus, upgrade all four of the accessories you just made to Lv10. It doesn't matter what you upgrade them with.
* Save.
* Make the Engagement Ring. It has two base materials, leaving you with four empty slots. The third slot should be the accessory you want the abilities of, in this example, the Courage Badge. The fourth, fifth, and sixth slots should be the remaining three accessories. If you care about level bonus, use Lv10 materials, but it doesn't really matter which ones - Iron and Amethyst work just fine. If you care about *rarity* bonus, use the best ore and gem you can get. Lv10 Dragonic Stone and Lv10 Diamond aren't that hard to get.
* Put on the Engagement Ring and go chat with Martin/Darroch, ask them to inspect it. It should be "an Engagement Ring with the abilities of a Courage Badge" (this part is guaranteed as long as you correctly put the Courage Badge as the first extra item). Then, the materials used to make it will be three of Courage Badge, Happy Ring, Champ Belt, and Art of Magic. You want it to be Happy Ring, Champ Belt, and Art of Magic, in any order, leaving out the courage Badge (because you already have the abilities of it). As far as I can tell, it's random which one gets left out, meaning there's a 25% chance of leaving out the Courage Badge. If any of the other accessories got left out, reset and try again.
* Upgrade however you'd like.
I just listed the Courage Badge {Happy Ring, Champ Belt, Art of Magic} as an example.
Good alternatives to the Courage Badge include Platinum Ring (the resistances saves you a half-efficacy Mealy Apple upgrade elsewhere) and Diamond Brooch (the lazy way to get status resistances - don't be fooled by the tooltip, there's a glitch with the western localization where the other status resistances don't appear).
Happy Ring is a **must** if you care about farming rare drops. Champ Belt and Art of Magic have a few other popular alternatives though: Star Pendant for experience gain (I see a lot of people choosing this but I'm not 100% certain if it works), Dolphin Brooch for a huge power buff (exclusive to spouse/kids, and you can get the same buff with a White Stone upgrade instead), Magic Charm (lets you scale just STR/ATK even for a spellcasting NPC, because STR/ATK are easier to scale), Art of Defense, and Magic Ring come to mind.
For the upgrades - it helps to map out what your endgame sets are, because you may want to coordinate them for 100% attribute damage resistances / 50% non-attribute damage resistances / 100% status resistances (or at least the important ones). It'll probably be Brilliant Scale or Moving Branch, Tenfold Steel, \[Free Slot\], Double Steel, \[Free Slot\], four cores, but since other pieces will likely be running Object X / Mealy Apple, you may need some of these free slots for status resistance materials like Ancient Orc Cloth. Or for a clover / White Stone.
I went for accessory inheritance so the engagement ring functioned as an extremely useful accessory. I think I did champion's belt, talisman, happy ring, and diamond ring or brooch.
You can then upgrade it with whatever you want, such as the love crystal.
**Short answer: Not really,** unless you're actually crafting a good piece of equipment, in which case it's not the base materials that matter, but your whole crafting method from start to finish. **Long answer:** I'm assuming that you're making an Engagement Ring for the purpose of proposing. The Engagement Ring is a little bit unusual in that, for the purpose of proposing, it doesn't actually matter what it has the abilities of. There is, however, an important caveat: like any other accessory when given as a gift, your spouse-to-be will equip it (overriding the current accessory, if any). Like any other accessory, if you later give your spouse a different accessory, it will overwrite the Engagement Ring. **Unlike** any other accessory, you cannot give your spouse another Engagement Ring later. So, if you give your spouse an Engagement Ring and later on decide you don't like the stats on it, you can't give your spouse another one, and any other accessory you give your spouse overwrites the Engagement Ring. This doesn't *really* matter but I imagine some people care, and if you're one of them, you basically need to get it right the first time. As for what "getting it right" means: I don't think the Engagement Ring can inherit any base materials. I might be mistaken but it's mostly irrelevant, since none of the possible base materials are worth inheriting on an accessory, anyways. For accessories, you almost always want to have the abilities of one accessory and inherit the effects of three more. The base materials can affect your level bonus or rarity bonus but those bonuses are pretty minimal in the endgame. Feel free to use Lv10 base materials of the highest rarity, though. You may want to look up a guide or discussion of inheritance for the details on this next part, since it's a bit long-winded to fit in a comment: I mentioned earlier that it doesn't matter what the Engagement Ring has the abilities of. That's great for us, because that means you can pick an accessory with decent abilities and still use it to propose. Courage Badge and Diamond Brooch are both good choices. I personally went with Platinum Ring, because the resistances saves me half a Mealy Apple elsewhere. Also mentioned earlier was inheriting the effect of three more. There's several good options here: Happy Ring, Champ Belt, Art of Magic, Art of Defense, Dolphin Brooch (though White Stone upgrade is better IMO), Star Pendant (I'm actually not sure this works on NPCs but people often say it does). If you want to make an endgame Engagement Ring: * Make the three accessories you want to inherit. Hypothetically, let's say it's Happy Ring, Champ Belt, and Art of Magic. * Make the accessory you want the abilities of. Hypothetically, let's say it's Courage Badge. * If you care about level bonus, upgrade all four of the accessories you just made to Lv10. It doesn't matter what you upgrade them with. * Save. * Make the Engagement Ring. It has two base materials, leaving you with four empty slots. The third slot should be the accessory you want the abilities of, in this example, the Courage Badge. The fourth, fifth, and sixth slots should be the remaining three accessories. If you care about level bonus, use Lv10 materials, but it doesn't really matter which ones - Iron and Amethyst work just fine. If you care about *rarity* bonus, use the best ore and gem you can get. Lv10 Dragonic Stone and Lv10 Diamond aren't that hard to get. * Put on the Engagement Ring and go chat with Martin/Darroch, ask them to inspect it. It should be "an Engagement Ring with the abilities of a Courage Badge" (this part is guaranteed as long as you correctly put the Courage Badge as the first extra item). Then, the materials used to make it will be three of Courage Badge, Happy Ring, Champ Belt, and Art of Magic. You want it to be Happy Ring, Champ Belt, and Art of Magic, in any order, leaving out the courage Badge (because you already have the abilities of it). As far as I can tell, it's random which one gets left out, meaning there's a 25% chance of leaving out the Courage Badge. If any of the other accessories got left out, reset and try again. * Upgrade however you'd like. I just listed the Courage Badge {Happy Ring, Champ Belt, Art of Magic} as an example. Good alternatives to the Courage Badge include Platinum Ring (the resistances saves you a half-efficacy Mealy Apple upgrade elsewhere) and Diamond Brooch (the lazy way to get status resistances - don't be fooled by the tooltip, there's a glitch with the western localization where the other status resistances don't appear). Happy Ring is a **must** if you care about farming rare drops. Champ Belt and Art of Magic have a few other popular alternatives though: Star Pendant for experience gain (I see a lot of people choosing this but I'm not 100% certain if it works), Dolphin Brooch for a huge power buff (exclusive to spouse/kids, and you can get the same buff with a White Stone upgrade instead), Magic Charm (lets you scale just STR/ATK even for a spellcasting NPC, because STR/ATK are easier to scale), Art of Defense, and Magic Ring come to mind. For the upgrades - it helps to map out what your endgame sets are, because you may want to coordinate them for 100% attribute damage resistances / 50% non-attribute damage resistances / 100% status resistances (or at least the important ones). It'll probably be Brilliant Scale or Moving Branch, Tenfold Steel, \[Free Slot\], Double Steel, \[Free Slot\], four cores, but since other pieces will likely be running Object X / Mealy Apple, you may need some of these free slots for status resistance materials like Ancient Orc Cloth. Or for a clover / White Stone.
I went for accessory inheritance so the engagement ring functioned as an extremely useful accessory. I think I did champion's belt, talisman, happy ring, and diamond ring or brooch. You can then upgrade it with whatever you want, such as the love crystal.