you do not do a turbo car on a budget!!!!!!!
Every build has it's budget, and this happens to be quite a reasonable one for his goals. If you did not "do a turbo car on a budget!!!!!!!", then 75% of the boosted Civics on here would be stock.
OP, I don't think you're going to be able to squeeze it in buying a kit, though. That Go Auto Works kit is the best deal you'll find for a complete kit, and it's $2000 by itself.
Turbo Kit - $2000
Vitara Pistons/Eagle Rods - ~$600
Tune - ~$300-400
Total: ~$3000.
It's not a question of whether or not you'll have to piece together your build. To reach 250 WHP reliably with $2500, you will have to piece together your own kit (recommended) or buy a complete used kit (not recommended). That's all there is to it.
For reference, here's a list I threw together one time, since I am also planning for boost. I didn't include the piston/rod combo, so throw that on top.
For EJ8 D16Y8:
Need (1st Priority):
Turbo
Wastegate
Manifold
Downpipe
Dump Tube
Air Filter
Charge Piping
Intercooler
Blow-Off Valve
Vacuum Hoses
Oil Lines
Fuel Pump
Exhaust
Catch Can
Engine Management/Tune
Injectors
Gauges
-Oil Pressure
-Boost Pressure
-Air/Fuel Ratio
Cold Heat Range Spark Plugs
Clutch
ARP Headstuds
Oil
Fuel
Turbo Timer
Need (2nd Priority):
Boost Controller
Radiator/Fans
Gauges
-Oil Temp
-Water Temp
-EGT
-Fuel Pressure
Oil Cooler
-Thermostatic Oil Bypass
Shift Linkage Bushings
Half Shafts
Brakes
Boost Timer
Differential
Maintenance:
Compression Test
Timing Belt
Water Pump
Head Gasket
EDIT: And as Kensai said, it may be worth your time/$$$ to buy the
non crucial, non high-wear parts used from someone who took a kit off their car, eBay, etc.
well besides the tuning part of it all.