with CB radio you do not need a license. You should memorize the 10- codes so you won't feel left out.
the best radio's are Cobra's, followed by Midland (IMHO) then Uniden.
Cobra's are a bit pricier, but they offer a lot of features.
you want to buy a radio that has switchable noise filters, RF and MIC gains, and a built in SWR meter. Having a single side band wouldn't hurt if you actually travel a whole lot. SSB is more costly, but you get upper and lower channels (80 total) and your range can be a lot further.
Best antenna is and always will be: 102" whip
But for most people, a firestick works very well. You can get a magnet mount or a hard mount, either will work just fine.
how long? as long as you want it to be.. but, at least 4' high. if it's going on a pickup truck and you have roll bars, then a 2-3' will be fine.. you don't want it to look obnoxious.