True. I always forget about all those factors. Still trying to run the whole wheel and tire stuff.
You'll first want to decide on how you're wanting your car ultimately set up. Are you wanting it set up for performance or looks? Are you wanting to run a certain wheel or a certain tire? OEM suspension height, lowering springs, or slammed coilovers/airbags? Given the 4x108 bolt pattern our wheel choices are relatively limited, and depending on which direction you go your fitment numbers can and should end up differently.
Obviously cost is a factor, but only you can determine that. Depending on your wants/needs, getting your hubs re-drilled can open up a larger wheel selection. If that's not something you're interested in you can usually get custom wheel offsets for no or a small fee but you'll have to wait for them to be made. That's obviously dependent on the wheel and supplier, but I ordered custom offset Pro Race 1.2's from PCA for my Mk3 Focus and only had to wait the three months for them to be made and shipped.
So I guess that brings up the final issue of whether you are looking for instant gratification or a tailored setup. The longer you're willing to wait the more options you have, and vice-versa.