Okay so. There's a lot of factors that go into this; make sure it's a gem she likes, not just diamond for the sake of diamond. Get synthetic; the entire "natural" diamond industry is a scam. It doesn't hurt to go with something custom, but keep in mind one important thing that I should have.

If your fiance is somebody who tends to lose things, go cheaper and get copies. I learned this the hard way, and it's a very painful lesson to learn. If she's some kind of scatterbrain or klutz, not to be rude but you need to be clinical about this, you're better off spending a couple of hundred bucks and getting like five of them and just putting the extras in a safe or something.

Because honestly the worst thing in the world is having her in tears because she lost something that important, plus the disappointment you will inevitably feel when she lost something so expensive. I know this is probably a niche issue, but you have to be objective about these kinds of things.

I have Moissy ring and it's gorgeous. I'd have been pissed to get something that cost more. It's really a pretty stone, and durable as fuck.

You will need an idea of her taste in jewelry, ask her literally to send you pictures of what she likes. I think a solitaire is best and that is way more affordable if it's not diamond, or at least that was true when we were getting engaged.

I saw a ring that opens beers… I’ve never a more useful engagement band.

Don't listen to commercials.... 3 months salary as a guideline .... My Ass!

By now you should know her tastes. Or just ask her about it. She's the one who's gonna wear it.

Yo! I will tell you what I did. I found a standard ring. Nothing fancy. Just a solitaire (ring with one rock on the top). The key part was that I went with a company that allowed trade ups. Meaning that I could return the ring for full price after the purchase as long as I was using the money to buy a more expensive ring. So I did that. Bought the normal standard ring, did the proposal, then went to get a new ring by trading it in so my partner could get one they absolutely loved.

IMO lab grown vs real diamonds are a non issue. They all look and act the same aside from having a laser etch.

For gold silver platinum, up to you. Again, you can always go standard and trade up (as long as the company does that).

I used a sapphire. I'm a ceramic engineer, and sapphire is just alumina, so I think it's cool, and you can get basically any color you want.

Alternatively you could consider something that isn't a ring. My fiancee is very cat coded, I gave her a gold cat bell that she loves and wears all the time. Got it from Mene dot Com which is a bonus because they're more ethical and transparent about their gold and pay which is something my fiancee is into.

You want a plain ring to go with your plain fiancée, is that how it is?

Next thing you know she'll be dreaming of a guy with wavy hair and chestnut eyes.