Part of the fun is to make a gradual progression on the modification path, in my opinion - from Stage 1 to 3 and beyond. Also, consider what the primary purpose of the car is - if this is to drive daily without any track duty, then I'd say - mild upgrades, easy on the suspension. If you do think that you'd want to track your FiST, then you will ABSOLUTELY need either a bigger radiator, OR more likely, a combo of that and an oil cooler. Things like cold air intake, catback exhaust/catted downpipe, intercooler, and a tune - that'w where i'd start. Suspension mods/bracing/braking mods - probably not needed, unless, again, you are planning on tracking it.
As far as worrying about warranty is concerned - I just had my car worked on by the dealer to get a braking sensor and an AC door actuator fixed, and brought it over with the Cobb tune flashed on, catless DP and all that jazz. No problem - unless you do put on some go-fast bits, like a big turbo, and there are some engine-related problems, I don't expect any guff from dealership. Clearly, brake pedal sensor and the actuator had nothing to do with the mods, so - got that fixed under warranty.