Well if your wanting to tidy up you solos then its a compressor your after. The noise gate is like an on/offswitch so when ever the output from you guitar goes below a defined volume it cuts the volume completely.
You know when you mute the strings with your hands, well theres always sum noises made isnt there, the sound of your hand scraping against the strings, well those noises are cut out.
I have a Yamaha SPX90, not that expensive. I love everything about it execpt the reverb. As ever Ive yet to find a decent reverb unit out there :(