Often, the best way to progress in a title is to train Rocket League Items with tutorials, which is right in front of your eyes. It may seem to be trivial advice, but some players, motivated by an urge to play as soon as possible, ignore the game's advice and "improvise": there is nothing more wrong to do!
Rocket League, in particular, offers a plethora of tutorials devoted to the different acts that can be implemented during a regular game.
To access this material, go to the Training screen on the www.lolga.com game's main screen and choose Tutorial or Custom Training.