As a rough guide of the bare minimum required:
excluding the cost of the turbo itself, your talking $400ish for a manifold, and $250ish for a kit with all the oil and coolant pipes for the turbo
You will then need a downpipe with a T25 flange on it, these can be had for around $300 in a fitment that will bolt up to your existing exhaust.
Some tweaking of the intake pipe is probably needed, and then you'll need a map which is going to be at least £400.
I recon starting with a standard car, and doing a lot of the work yourself, you're looking at around £1500 just to get it running.
Ideally, your going to want to put a bigger intercooler on, and probably change the exhuast out for something better, so will need to spend a bit more. You will also need a set of injectors and probably a 3" MAF housing if you want to get decent power from it.
Could easily spend 2k+ if your starting from a stock car, although shopping around and buying used etc where possible could see that dropping down a bit.