First of all, a Martin 00 does not have the same depth as a dreadnought, it's shallower.

Secondly, buy a good capo. Not a clamp-on type, because they distort the string spacing and pull the guitar out of tune. Paige is very good; Elliott or McKinney's the best, but way too expensive IMHO. I use my Paige, exclusively.

Thirdly, don't agonize over being able to barre chords. Many great guitar pickers don't even use them. Learn how to play the basics, well, then, after a while, if you're still of a mind, work on the barre chords. If you take on the really difficult stuff, first, you might be setting yourself up for failure.

Best of luck.

Owner of Paige, Shubb, Victor, and Kyser Capos.