If you prefer to watch videos instead of reading the guide, feel free to do so. There is a playlist that covers every trophy on my YouTube channel. If you'd like and subscribe or even become a member, it would mean a lot to this channel!
The first step is mainly about getting to know the basics of the game while taking a look at all 12 tracks the game has to offer.
This step takes roughly 2 hours to complete. We need to win all 9 cups on Rookie difficulty. You are going to visit every track three times during this step. Whether you use this time to practice the tracks and improve your lap times is up to you. I would recommend it, but it is not necessary :)
This step is the most annoying one for me personally. It requires us to do the same 9 cups we completed for step 2 again, but this time on Elite difficulty. Why they didn't make the trophies stackable is beyond me. Luckily winning on the Elite difficulty is nearly as easy as it is on Rookie diffculty.
By now you should have won 18 cups and have a good feeling for what is necessary to beat the Elite AI. If you're looking forward to do something else than racing in cups now, I have some bad news for you. We need to win 10 more, but this time it has to be done in Online Mode. The servers are deserted, but the good news is that the game has Cross-Gen support. That means if you have a friend that owns this game on PS4 you can create a lobby together. The rest of the field will then get filled with Elite AI drivers. You can deal with them the same way you did in step 3.
This is the final step and the only skill-dependant one of the game. To complete it, we need to beat all 12 time trials, one on each track.