The ideal setup (in my opinion):
ProVari Mini
Extension cap
Tatroe ProVari Ring (extension)
ProVari Ego Adapter (510-eGo)
It's made of stainless steel and brass, unlike the chinese pot metal versions, this one won't break.
AW IMR 18650 Batteries
AW IMR 18350 Batteries
Xtar XP-4 Charger
or, if you really want the best, the
Pila IBC Charger
with the options listed above, you can get a ProVari Mini, and still be able to convert it into a full size ProVari. With the eGo adapter you can still use Mini Novas, Kangers, and everything else that works on eGo mods on your ProVari. I've heard great things about the Pila charger, but I've also had over a year of trouble free operation from my Xtar charger. The one area you don't want to compromise on is the batteries. Use only button top IMR batteries (they are unprotected, but use a fairly safe chemistry- they won't catch on fire or explode like Li-Po and Li-ion batteries can).
RTD Vapor used to have the best prices and selection of batteries, I don't know if that is still true.