first congratulations on getting a mark x, second what version is yours? now I want you to understand that mark x doesn't have lots of tuning potential like JZ engines or etc its a Aluminum block and head, now if you 300G premium then you're gold, get a 2GR swap in that it'll set you around 315+HP or better yet get a supercharger kit that'll take your 250 hp to 310s, what you need is 2GR and a 4GR transmission and 3GR PREMIUM ECU, then get a LSD brand new is recommended, Lexus Is350 cold airintake and a original good filter, A free flow custom SS piping exhaust, and a proper tune to get them working properly. I'm saying this considering you have done all your maintenance which includes, all oil changes, 1) Engine oil 5W-40 is recommended if your engine doesn't eat any oil. 2) transmission fluid Toyotas genuine one. 3) Diff Oil: Toyotas genuine LSD oil. 4) Tri-Tip original denso spark plugs, new fuel pump, brake oil, AND remember to get all diff bushings changed as powersliding and drifting puts a lot of stress on them, And lastly Get a Big Brake Kit preferably a Is350 one import from Dubai.
Now let's cover the cost of all these
liqui moly 5w-40 engine oil 1600 per litreX 6.3 litres, transmission oil 1500 per litre X 8 litres
diff oil 1.15 litres
diff bushings 30K
total cost of maintenance =60-70k
custom made SS piping exhaust 30K
custom made SS pipe for intake with sensor if you can't get your hands on is350 intake: 15k and 15k for the filter/ but if you want to go for the K&N cold airintake for is 350 it'll cost you around 50k with filter and import,
Now what depends is that you want a 2GR or 3GR supercharger kit, 2GR head assembly alone will cost you 200k-250k easy, 4gr trans will cost 30-40k and 3GR PREMIUM ECU will be needed to be modified that'll be easily 50k. or if you want a supercharger kit first that isn't available in market as a kit HKS has some that'll be 5-6 lacs easy, or you could buy a NCP and take its engine and supercharger there are many superchargered NCPs in pakistan, they go for like 10-15 lacs, a is350 big brake kit will be 60k with 2 pairs of brake pads one set of rotors and everything import included. LSD can cost a lot of lot less depending of what you get and from where a supra mk3 torsen LSD will cost you 50k and a good tune 50k easy, now including everything the labour cost will depend on where you get them done from go to maxpower or some other good garage, because they do know what they're doing. And you'll need a good set of coilovers 50k labour 100k-200k max. NOW everything will be done in a Million. after spending a million you'll be standing on 350+ HP and good ass mark x