I suggest trying some out...for a long time, before you spend the money on a compressor. Some guitar players CAN and DO get by without compression...if you like to use "dynamics" with your playing, I suggest staying off the compressor. If you're more of a lead player who wants more sustain (and who doesn't want that?
just kidding!
) then try out some compressors.
Personally, I use a simple MXR Dynacomp...more as a booster than anything else.