Don't try to cut corners by going for the lowest fps possible. All you do is end up with a craptacular gun. Most guns (excluding AEPs and airseal problems) with a stock fps below 250 can't be upgraded, and tend to have poorer rate of fire as well (if electric). Shop by brands that have been reviewed to be good for their price and aren't upgrade-deadends.
What is your budget, anyways?
"The Bird of Hermes is My Name, Eating My Wings to Make Me Tame."