I'd say keep saving up until you have a good cushion to whatever you decide to do. Let's say you go the nitrous route, save up enough "just incase" you blow the motor afterwards.
Just buy a blower and run the tune that comes with it. It will be safe and you shouldn't have any issues out of it.
Do not waste ANY money on NA. FI to 400whp and be done with it. You could go up to 450whp, but it would cost a little more.
Bingo.