The Garret GT2560 is a ball-bearing turbo that came on the Nissan 240sx and Silvia, this means alot of people sell them for cheap when they upgrade. If youre lucky you can get one for 350$, the rebuild kit is 120$ of ebay. You can get good quality aluminium t3 manifolds of the Mazda 323 GTX Facebook group for around 250$, you could reuse the stock blow off, or upgrade to a electronic system. GFB makes a good boost controller you can get for around 150 used or 250 new. For the dump pipe Id have a turbo shop make it for me I wouldn't expect it to be over 280$.
If you got a non electric blow off you could save alot more, but as it stand it would be 1150$ for just the Turbo, dump, and boost controller. You'd still need the fittings for the oil drain,piping and a larger intercooler. That turbo however can give you up to 300hp on a good tune. You could probably get everything for alot cheaper if you were good at scavenging things from the junkyard, and searching ebay really hard. In the coming months ill be starting my turbo build. I plan on detailing everything on my build thread.