When you start playing Rocket League, start by playing a few round Unranked.
After doing this and you got in touch with the movement etc. start playing training packs.
There are hundreds of training packs which offer training for one or more techniques.
Try playing them to get better with different mechanics.
It needs a lot of patience and training to achieve some progress but after finishing the basic training, I recommend starting to play Ranked.
Also start watching YouTube Videos about Rotationd and Pressure and other mechanics.
By playing extra modes you won't really get any better so I won't recommend playing them.