Give us a hint
It's literally just buying new Supras from the store for 55k, then spending 5 skill points in their tree. 1 point gives you a small amount of exp (these add up and will level you for a few normal wheel spins), 1 to path to be underneath the super wheelspin node, then 3 points for the super wheelspin itself.
You don't even need to leave festival, just buy the car, immediately use the points in the tree, then buy the next. All the wheel spins can be opened in bulk once you leave and you can simply remove all the cars you have from the garage once you are done so it's not clogged up. I clocked up a couple of hundred skill points in the formula drift cars and started buying Supras with 600k in the bank, I bought 10, used the wheelspins and was then at 1.2 million. Repeated a couple more times in large numbers and was at 5 million.