yeah, tons of info here, differences between models. probably at least spring for a well known one.
but my quickie advice is the beefy 1000maH ego battery that fits 510. That's a decent atomizer, even though i like LR306 attached to it.
That's what I've settled on a year in and wish i'd started with that. although you could make a case for something like the 808, maybe from vapor4life being a better choice for newbs.