Congratulations!
Setting a price limit is a good place to start/an important thing to keep in mind while you browse. Remember that you'll wear the dress ONCE. (I still have mine, after 29 years, hidden away somewhere, and I think I'll eventually donate it, now that it might be back in style.)
Consider this: Have you worn formal dresses before that you liked? Or didn't? What elements would you keep or change?
Have you seen people on tv or in movies wearing dresses you really liked or hated? Even if you weren't thinking about it, there might have been something that jumped out at you as "Wow" or "UGH!!" For example, think of all the weddings on Friends; there was a lot of variety there, and a least one of them has to have you thinking, "epic meh," at best. Take note of that stuff!
The next step is to find out what wedding dress(es) actually looks and feels good on you.
If your David has actually seen you in the types of dresses he mentions, definitely take that into consideration, but also know that if you don't like what you're wearing, that will show on some level--unless you care to fake it.
Some personal examples you may find helpful: I'm not a dress person but after browsing a lot of magazines (no internet then--amazing!) I had in mind some features: off-the-shoulder but if possible, with sleeves that would make my relatively large (but strong!) upper arms less conspicuous for the dainty occasion. I like a princess waistline on me, as I'm a mesomorph; the dress I picked both highlighted my slim waist and gave made me look a little curvier. I wanted a little train, but not a big one, and the tailor/seamstress rigged it so that we could hitch it up and hang it from my waist during the reception--pretty and practical! I wanted some sheen and lace, but again, not too much.
Then it came time to hit the streets: I browsed dresses in a couple of stores and stuck with a chain store with a bigger variety and much lower prices. There, I narrowed it down to two or three which I tried on. I made an appointment with my Mom and maid of honor: I tried on the dresses again and measured the reaction (including my own again). I think we eliminated one right away, and the final choice became obvious at one point. I went home quite excited! I was sure my fiance (whom I'd known for almost 7 years) would love it, and man was I right!
Pro tip: the photographer's assistant set off a few flashes as people first turned to see me; my husband said the effect really blew him away.
I hope you're able to take your time and enjoy the process. If you're in it for the long haul anyway, why not?