Spending garage points: engine or tyres
On a twisty track, tyres come first. Engine power only pays off once you can exit a corner without losing speed.
On a twisty track, tyres come first. Adding engine power before the tyres are good enough only makes the car faster into the corner and much wider through it. Time lost off the racing line is far larger than time gained on the straight.
The efficient order is usually: tyres, then brakes, then chassis or handling, and engine last. The exception is a long straight with one or two slow corners, where engine power genuinely pays back sooner.
Before spending, check whether points can be refunded. Some titles allow a free reset, and that changes everything: you can try two different builds on the same track and keep the one with the better lap time rather than the one that sounds faster.
Also check whether upgrades apply per car or to the whole garage. In titles where points are per car, spending everything on the first car can leave you stuck in the next race, which uses a different one.
Do not chase the highest number on the stat bar. That number often does not match how the car feels on track; two timed laps tell you more than any bar.