your basically asking us to throw coins in a wishing well so you can pick one. There are the originals which will cost you quite a bit, clones which can be had for cheap.
Stay away from complete kits on mechanical's unless it includes some good named
batteries like sony, mnke, aw imr, or efest. Most kits will come with cheap no name batteries, which are very common to see on FB with my mod is destroyed.
as far as which to buy the nemesis, k100, chi you are very popular but those are just a snap shot of what is out there. take a look at the thread that shows of mods, find something that looks nice, and learn more about it is the easiest way to go about picking.