build a 300+ whp GT?

Okay introduction.. I have almost no experience in building customizing cars I'm willing to work on my car but must do it under supervision.

I have a 91 turboII with a rebuild engine with 10K km on it..
My multi year plan is to build a GT with 300+ whp..
but how should I plan to do it?
I already have a 3" exhaust but I need an extra silencer..
should I wait an save up some money and buy the lot (standalone ECU, turbokit, fmic, engine with 3mm apex seals and streetport, injectors) but what costs am i looking at to get my goal?
Or should a start now with removing stuff like emissions and AC and then put a standalone + boostcontroller on it.. and when I got cash I buy other stuff and put it on rightaway..
btw.. brakes also must be replaced by something better.. and there are some minor electrical problems.. shocks + springs are going to be replaced soon..

I'm curious how some of you build their cars and what they learned of it.