For the best Stage 1 performance, I recommend the following:
VIS HPFP internals
S3/6R intercooler
New fuel filter
New plugs - BK7RIEX
Red coils
Go fast Bits DV+
0W40 Mobil 1 oil
PiperCross dry foam panel filter
PowerFlex engine and gearbox mount inserts
Vibratechnics Dogbone mount
Precat delete
That lot should bag you around 310hp on an Edition 30 and 260ish on a K03.
You only need a downpipe, exhaust and induction kit for Stage 2/2+. Well, I say 'need' but that's what the tuners selling you parts will tell you. I've run 2+ with the standard exhaust, DP and engine cover without any issues.
Revo sell many things, so 'upgrade' can be software, brakes, intake etc.