That's a tough one Scott as there are sooooo many devices out there right now. personally, as of this minute, I would suggest a box mod that puts out decent wattage and also had temp control as an option as I truly believe that is the new direction of vaping. Something like the new 80w Smok box mod fits the bill there and is budget friendly.
As far as a tank you need to be a little more clear on what you mean about rebuildable. I would suggest, based on what is available and will fit both your budget and experience level, something like the Kanger Subtank which can either use heads (which are easily rebuildable themselves) but also has a build deck much like a Kafun style RTA.
For an RDA that also depends on your style. You can get an authentic Mutation X or CLT for pretty short money and they are cloud chuckers for sure. Other RDAs like the Plume Veil, Hobo, Derringer (more flavor chasers than cloud machines) will cost considerably more unless you go the clone route.
Hope this helps and just my $.02 for today that is...lol