Welcome to the forum, @pastiez!
Let me start with a link:
The general rule of thumb for a new player is to not rush with 4 and 5* heroes. Your resource base is not yet good enough for that (recruits, food, iron, ascension items). Focus on 3* and build at least one fully ascended rainbow team of 3* heroes. After that you can continue with 4*.
Alternatively, you can bring a rainbow team of 4* to 3.60. In most cases it will be more powerful than 3* team and it will have a potential to grow to final ascension when mats are available. The drawback here is that you won’t have heroes for rare challenge events.