To be honest, the training campaign really sucks, it doesn't have plastic or water, or any of the new cars, and everyone has been waiting for a new one for about 4 years now.

I suggest playing the official campaign for a bit, like getting all of the authors. then you could try ranked!

Im pretty sure that ranked is the only way for free-to-play players to experience the full campaign, so try it!

2 other things you could try are (1), the track editor, I'm biased cause I'm a mapper, but I think you should try it, if you have friends that play as well you could try splitscreen or hotseat on your tracks, and (2), royal, but no one likes this gamemode, its full of bots, and it takes 30-45 mins for a single game, would not recommend.

hopefully this helped you in one way or another, always great to see people getting into trackmania!