First I should point out that stages mean different things to different people, so I'm going to assume you are after first step starter mods that you can add one at a time.
You've not said what car this is for so I can only speak very generally.
Remaps always add more power than any other mod for the money on a turbo car.
Exhaust and intake improvements and suspension upgrades are all good starting points IMHO.
Camshafts are a good power mod for NASP and TURBO engines, but they require the head off and some specialist skill in setting them up and checking the valve clearances so I would regard that as a stage 2 mod.
I hope this answers your general question about stage 1 tune ups, and hopefully we can answer any more specific questions you may have for your car.