Nissan SR20DET engine

As most turbocharged engines, the SR20DET is capable of developing more power without spending an awful lot of money on the project. Here is the list of parts you would need to run a safe 380hp on your engine without building it from scratch:

Pistons: if you have a healthy low mileage engine, it is not required to fit aftermarket ones.
Conrods: same as above, standard conrods should be able to take upto 450HP on standard rev limit.
Head gasket: the standard 1.1mm head gasket should be good for boost upto 1.6 bar or around 420HP.
Head studs: always replace the head studs when rebuilding the engine, or you risk the chance of them streching which results in head lift at higher power levels. ARP head bolts are good upto 600hp, OEM ones seem to slowly strech above 350HP.
Valvetrain: check the condition of the valves, shims and rocker arms and replace if there is to much wear or if you like to bang on the rev limiter. These parts seem to wear out quickly above 350hp too if they have never been replaced. Weak valve springs are not that uncommon and can lead to severe power loss at higher RPM.
Injectors: Nismo 555cc ones or 730cc if you'd like some reserve with fueling.
Air flow meter: the 300ZX Z32 orange label AFM is a popular upgrade. Requires a suitable air filter.
Camshafts: standard ones are good for around 400HP, anything more would require a turbo with more lag, so upgrading cams is almost needed. You should get away without needing a remap with 256° or 264° ones and still notice gains. Uprated camshafts may require stronges valve springs and matching retainers. Some aftermarket camshafts retain the VCT system.
Turbo: the Garrett GT2871R is a straight fit, available in .64 r .86 exhaust size, both should reach 380HP comfortably and could be pushed to 400-420HP with the right supporting mods. Holset HX30/35 seem to be used too, but there are no premade chips or maps available for these turbos, so will require a custom map or standalone ECU.
Intercooler: due to the small size of the standard WMIC, it is important to fit a front mount intercooler.
Clutch: an aftermarket ones will be required as the standard one struggles even when increasing boost on a standard T28 turbo and getting around 250hp.
Spark plugs: 2 grade colder ones are required, NGK copper BCR8ES should do the trick, all 4 for the cost of an iridium one if you don't mind replacing them every 10.000 miles or so.
Coilpacks: standard ones work fine, but are prone to failing. You can get 2nd hand ones cheap or get Splitfire ones so you don't have to worry about them anymore..
Exhaust manifold: the standard exhaust manifold becomes very restrictive above 350hp, so it would be a good idea to replace it with a stainless steel one. Try to aviod cheap ones as they'll most likely crack very soon and also keep in mind that not all manifolds retain the same position as the stock one, so you might need a matching elbow too.
ECU / mapping: for 360-380hp, the easiest way is to buy the Horsham Developments stage 3a ECU upgrade, which is a perfect match for the above setup (but only for nismo 555cc injectors, it would work with the larger GT2871R 0.86 turbo but wouldn't be ideal).
Fuel pump: an aftermarket fuel pump is needed when increasing power, the Walbro 255L/H pumps are popular. Should be one of the first mod anyway.
Oil: use good fully sythetic oil and change it every 4000 miles if you drive hard, otherwise every 6000 miles would be ok too..

IMPORTANT: when increasing power, it is crucial to upgrade the cars suspension and brakes, so try not to spend all the budget on just engine tuning parts!