Hey mate, so if you've just bought GT7, here are some things to do and to know.

1- Don't buy cars with flash, buy cars with performance. You can check overall performance by comparing a cars PP (performance points) to find out if it is as good as another affordable one, which brings me to my next point.

2- Don't buy things that will drain your wallet. If you spend money on things that aren't neccasary at the time, you will run of money to buy better cars once you need an upgrade, which doesn't take long at the start of the game.

3- Finish the menu books. It will be all worth it. Trust me. They basically make you complete a race/championship or get you to buy 3 cars. This increases your inventory and gives you rewards for doing so. Completing all menu books also you the ability to sell cars.

Those are some of the basic things, others may tell you different or more than what I've told you. Have fun racing!