Possibly one of the hardest games to play if you do not start out with researching every inch of the game. Like most MMO mobile games there are way too many things to learn and shortcuts or little tricks to make things easier.
When starting the game, try to boost yourself, if you are a F2P, even if you are not a boost is good, so don't lvl too fast, stay below the castle unlock and move to a new kingdom as it opens up, this way you will be ahead and be able to join a really good alliance. Joining an active alliance is just as important as joining the best alliance.
Commanders are the most important part of this game especially your legendary as a F2P it will cost you months or game time to fix a messup here so start out right. Here are a few helpful sites :
https://rok.guide/talent-guide/
https://rok.guide/upgrade-commander-skills/
The rest of the game is pretty forward and your alliance members will be able to give you guidance on the rest
Best of luck to you all