The MVP 2 in my opinion is probably one of the better "budget" priced mods. It has a large capacity battery, is very solidly built, and really hard to beat at its price (You can find it on line for about $40).
Its voltage and power ranges (3.3-5 volts, 6-11 watts) while not as "powerful" compared to some
devices is still more than enough to allow you to have a great vape with a wide range of toppers and most rebuildables (depending on how it's built by you).
I have a handful of "variable"
devices and my MVP2 is still one of my favorite grab -n- go devices.