Do the go kart. Learning or cultivating some real hands-on mechanical skills will serve you well over the long run.
Hopefully summer is coming in where you live. Go outside and enjoy some "shade tree" mechanic hours. Scrape and bang up your hands - be proud of the scars. 🙂
Then drive around as the laws permit.
Besides, PC prices are going down. If you wait awhile and continue saving you will probably be able to build the pc sooner than you think. You can do that on rainy days and learn another skill set. And there will be some overlap.