Hello everyone! First of all, I'd like to say that I'm a total noob to writing songs, so go easy on me

If things work out, I'll be joining a band with the aspirations of being an ambient/experimental rock band. Since this will be my first real band, I want to have some kind of knowledge base of how to write songs (or at least progressions) that transcend the basic I-IV-V ect bluesy/rock sounds and have more of an "epic" feel to them. Now my question is.. what chord shapes would you all recommend to achieve this type of sound? So far, I've found that dominate 7/9/11/13s give a nice full sound, but maybe a little too jazzy. Any kind of input would be greatly appreciated. I'm a wanna-be theory guy, so if possible, throw it at me Thank you in advance!

p.s. Any recommendations on great pedals to achieve really cool ambient sounds would be appreciated as well :P
Ambience can also be helped by effects; a few of my more "epic" introductions, if you will, use delay and chorus to fill out the sound (with a little whammy bar action as well) and give it a nice ambient feel.
So basically, I should be aiming towards the overall tone to produce a more epic feel, rather than specific chord shapes, eh? Hmm, must go pedal shopping then!