This one is fairly Easy, the first two races start off simple much like Sprint and super sprint and then get harder on the third race.
For the first race don't use boost at all and try to get as many item pick ups as possible, spend cash on accelerate and engine, if you have the cash buy some boosts.
For the second race, same concept if a boost is absolutely necessary go ahead but save them for stretches and don't use more than three. same buying strategy.
I entered into the last race with about 40 boosts and got 1st place by about a half a lap. save boosts for stretches and keep corners tight while prioritizing control.
It may take a few tries but you'll get this one fairly easily.