If you want something small since your a very light smoker, you could try one of the smaller pv's like a KR808 or a 510.
KR808- Vapor 4 Life, Volt, Bloog. They're small, cigarette size, battery lasts a couple hour 2 piece pv (carto & battery)
510- Similiar to the KR808 in size. Can be used as a two piece (carto & battery) or three piece (cartridge, atomizer & battery)
You can get a good brand from one of the registered vendors for $35-$45. To start out with, I'd get 30 ml of juice and a box of cartomizers for the KR808 or the 510. I'd also get either a pcc (personal charge case) or some extra batteries. All of this will definitely be under $100.
If you want a bigger battery pv that lasts longer (8 hours) but doesn't look like a cig, an ego is a good pv. You can get one for about the same price as the 510 or KR808.