tough call...dont really know your terrain. i would suggest riding a gear that you can spin pretty comfortably on log stretches and still make your climbs. riding a fixed gear bike on rolling terrain is kinda like riding built in intervals. you will be amazed at the hills you will be able to climb eventually. find several climbs of different difficulty, and practice.

put your ass back in the saddle for power and sit for as long as you can. when you stand, work the bike hard, and try not to lose momentum...as i slow i guess i focus on the backside of the pedal stroke, pulling myself up the hill, anybody else think like that? do whatever you have to, dont stop. get to the top of the hill with your eyeballs hanging down around your waist, snot hanging off your chin, and barf in front of that woman walking her golden retriever...spin your legs out on the decent and repeat if neccessary!

cheers