Firstly congrats! You've picked a beautiful car, had mine for bit over a month now and i love it more than my girlfriend.
Secondly you will get more accurate replies in the V-Series Skyline section. I'm investing in Motordyne Shockwave TXD V2 but it really depends how much you want to spend, if you have found the setup that you really really want (in my case) do a bit of research and see if you can determine which one is going to give you the most bang for your buck. Brands that i know and trust would be ARK, Motordyne, HKS & Fast Intentions.
Goodluck bro!