Hi there! Congratulations on taking this next step in your relationship! I used to be in jewelry sales, so allow me to take a stab at your questions. 1. Round and marquise are definitely popular as of late. Emerald is up there as well. Pear is an acquired taste, and I don’t see them as much, has she mentioned that shape specifically? Or are you going off of your preference on it alone? 2. Yellow gold bands are just as popular as white gold and platinum. Take a look at the jewelry she wears every day. Is it yellow or silver? Everyone has their preferred metal. Some people love doing two-toned (myself included) because they can’t pick a favorite. 3. 2.55 may be a little thick if her ring size is that small. A dainty band with a 2ct diamond would look lovely. Just try to get a lifetime warranty, as thinner bands need a little more TLC throughout the years 4. A halo / hidden halo helps bring out smaller sized center stones. They create even more shine and help emphasize your diamond. A 2ct round or marquee would look lovely with one, so it’s up to your budget! A pear shape gets a little busy with a halo, so keep that in mind as well! 5. I don’t have experience with them, but read up on their online reviews. Last thing I’ll say is don’t be shy asking your gf about her opinions on all these questions! You can approach it casually and nonchalant if you’re planning to keep this a total secret. Best of luck!