Do a search on posts by 'Fubar'... he is the master of squeezing good results out of the cheap ebay setups.

The two biggest success factors are:
1) find a tx/rx with channel SWITCHES. Avoid the ones with a tuning knob.
2) use a ccd camera instead of cmos. cmos will get you in the air ok, but ccd will make it shine. Expect to pay more for the ccd camera than you did for the tx/rx set!

Good luck,
Bill