There is a difference between performance items and estandard but as said, varies from engine code (and turbo).
The DV you want to get is correct, check with R-tech which spring you need (as it comes with several). Induction kits vary, the pipercross filter and green cotton filters will not ruin maf, what it is, is the K&N and other branded filters are oiled/greased up, this upon intakr ruins the map, could always wash them

Id get remap first as I'm pretty sure if you get exhuast done later you will still benifit the same way from the remap regardless of before or after. As for cheaper option, it's building your own exhuast or going elsewhere for one eg blueflame etc...