Where can I find an engagement ring that will neither fall apart nor financially ruin me?

My girlfriend and I have been talking about marriage for a little while now. (We're both entering our thirties and live together, so despite the finance stuff this isn't some ill-advised kids thing.)

I have a dead-end municipal job in a small town, which I've been trying to get out of but it's a tough job market. I also have a ton of student debt and some medical debt; long story, but basically making ends meet has been rough for me. She's in trade school, on track to make a decent salary (like 20k more than me) once she graduates this fall. I was holding off on proposing until I could at least afford a traditional ring in the few-thousand-dollars range, but when I mentioned that to her she said "you could propose with a ring pop and I'd say yes!"

So now I'm shopping. I know she doesn't mean a literal ring pop, but I think it's safe to say a traditional diamond isn't necessary here, and lab grown is fine – we're also both pretty well informed on the ethical issues with diamond mining so I honestly do not think she would want a traditionally mined diamond anyway, nor would I want to buy one, really, unless it was an antique. But lab grown can still be quite expensive, partly because of the material of the ring itself — I don't want it to turn her finger green!

I looked into Modern Gents but they sell rings for less than $200 each which feels wayyyyyy too good to be true. Renaissance Jewel, Molly Jewelry, and Rare Carat all seem like better options but I'm still wary of all of them because I don't know them.

I guess I have 2 questions:

1. How much should I expect to spend on a lab grown diamond ring? (And what's the lowest that number could realisticaly be without seriously sacrificing quality?)

2. Does anyone have experience with any "budget engagement ring" company like the ones I listed? Are any of them trustworthy and high quality?