I worked on my 3* for a good while before moving up.
Once you get 30 you can compete in the 3* tournaments and events which will start to give you the bits needed to work on 4* and into 5*
Still today I work on 3* too. Having a good set of 3* heroes never ceases to be useful.
Then as you get more into the game you can start to look at your 4* and eventually you’ll start to pick up 5* too.
We were all new once and it’s a pretty daunting spot. Also there’s a pile of training alliances that will take you in and help you to get better. Check the recruitment threads out.
And never be afraid to ask questions. The forum is full of very knowledgeable people who are happy to help you.