If it's the hardware that's limiting, i don't think there's much tips that can be given. I just ended up selling my Surface Pro 3 because it felt awkward to use after being spoilt with Cintiqs and Intuoses - and that one at least has pen pressure. iPad doesn't have pen pressure unless you've got the new one, so that is pretty limiting - best way is to optimise your style to work with it. Sometimes limitations really help creativity
I've done some of my favourite sketches in Tegaki a (now closed I believe) oekaki-like website with the most basic of drawing tools.
Other than that..there's always paper?