if you game start a game server or like you said turn it into a NAS but a NAS doesnt take very much horsepower. I personally recommend having a nas and a render machine in one box.
Welcome child! And no computer can be future proof. Personally if you are only gaming at 1080P id recommend at least 8Gb ram something like a i5 or even i7 and something like a 960 or 970 ti with about like a 600-700 watt psu if you want to upgrade your system and dont want to upgrade the PSU as often.