ok a turbo on average for a new good one is $700 so you even if u can get boost gauge, piping flanges and intercooler for $300 u are still short a lot of parts.
wastegate: ~$200
oil lines/fittings: meh lets say $50-75
gaskets: lets say about another $50
good couplers/clamps: $100ish
general welding for piping and flanges: $75
injectors: $150ish
fixings shit you fucked up: about another $100 but probably more
so thats another $750
300 + 700 + 750 = $1750
plus i am probably forgetting things