If you want to rent kites, don't bother buying a bar.
Personally, I would rather rent a board and bring my kites. Kite rentals are becoming more widespread, if that's the word, but are still hard to find. Plus, with some experience you'll find it annoying to have to adjust to a different kite every time (I would).
I'd buy two kites: a seven and a nine, and rent larger kites when needed and possible. Or seven and ten, eight and ten, eight/eleven.... really depends on your weight. You could buy a foil kite, which with time and experience will give you a massive windrange....you could do most of your kiting with one kite, plus they're incredibly easy to pack.
Good question, hard call.
Maybe the best answer would be to ask yourself this question again, when you're a better kiteboarder.
As far as a good harness goes: there are plenty good brands out there. Best is to go and try some on. Good fit is everything.
Welcome to your new life