Or this lol. KD’s guides will help you to build a team/strategy and progress in-game, but there is still more to it. Really, my advice depends on your focus. If you want to improve at PvE, I’d recommend trying a some kind of challenge or restriction(such as only using one element). This will allow you to learn to counter the challenges of PvE through trial and error, which is often the best way to get an intuitive understanding. Challenges such as my 7 trials may be a bit extreme for a newcomer, so try to start with something that limits your monsters, but not your playstyle, such as not using the online section, or only using a certain type of monster(like bird or lizard).
If you want to improve at PvP, I’d recommend watching pros battle. There are plenty of videos available, and they will help you to improve. You could even see if anyone is willing to battle, and I’m sure that a few people will agree