If you are looking for
tank style i have had awesome luck with the Smok Aro II, its pyrex so no worries about tank cracking juices and they are about 4 bucks a pop, Nautilus is amazing (just watch out as crappy clones are popping up everywhere) or the Kanger Protank 2 with the Aerotank base works great or if you never want to worry about leaks again then go RDA but having to re-drip can be inconvenient.