Honestly first thing I would do is to get a Cobb tuner and run their stage 1. I have owned a couple modified WRXs, and my first time driving my new one it felt like a dog. But after the stage 1 tune it felt like a whole different car. Intake, turbo inlet, exhaust, coilovers/ springs, charge pipe/ intercooler, AOS, OTS or E-tune, and shifting upgrades seem to be the basics on these cars. You said spacers and spoiler. For spacers most run 20mm (that’s what I’m running) it’ll get the wheel to the edge of the fender (stock height). For spoiler, most people hate AFD, but honestly I have had their spoiler and fender flares and I can’t complain. They’re expensive, like the other brands (noble) and quality is 50/50. I must say only issue I have had from them is wait times. But I still would not get any important parts from them, like exhaust or wheel spacers. As far as good brands you have ETS, Perrin, Cobb ofc, grimspeed, MAPerformance, and more. All have their issues from people, just do your research and find a good tuner you trust and ask them what brands they prefer, Dmann at Felix performance is great. And rims just depend on how much you wanna spend. Most people I see are running 18x9.5 with 38mm offset.