I've always hated playing through FF games without a FAQ because of the sheer amount of cool stuff you miss out on if you aren't specifically looking out for them. Is 13 similar to games like 9/10 with the amount of optional sidequests/weapons/items that are easy to miss? I know the game is pretty linear for a long time, but should I start using a FAQ once the game opens up later on?

Keep with your tradition.  If there is one FF in which you don't need a FAQ, 13 is indeed the one.

I had the strategy guide and loved it, I'm unfortunately horrendous with RPG's without one.

I only used a FAQ after beat the game so I could find out what missions unlock the fucking chocobos!

You could very easily beat the game without a FAQ, but if you're into Trophies/Achievements, you'll definitely need help for the last couple. Here I'm thinking of the Weapons/Accessories trophy. Wow.

Nah, there's no need for an FAQ. Just be sure to pick up everything, which isn't hard at all.

i am just interested in the 8-16 hours of mediocre game play before the game actually gets good. Oh wait! I want the androgyny too! 

you wont need one.