RC electric or Nitro car advice

viccig

Hi everyone, hoping for a bit of advice please.
My son is 14 and massively into fast cars (he's autistic so I mean really really into them!).
Anyway I know you can buy some fabulous rc bits of kit, he doesn't know they exist so I want to surprise him with one for Christmas.
The problem is I don't really know what I'm looking for- ideally I would like some sort of beginner kit that he can build and learn as he goes with the option to upgrade parts over time.

Does anyone have any pointers of good websites/starter/ build it yourself kits?
Budget isn't huge (max 150) so I assume it would be a basic setup to start with. Not overly keen on 2nd hand as I really don't know what im looking for.

Any help would be appreciated.
Thanks