Welcome to the game! Be prepared for the long haul, this is a game that takes months to develop your teams. You’ve done a big step coming to the forums and you’ll be leagues above the masses in no time with what you can learn here.
To your original question, it will make progressing easier by leveling a rainbow team first.
For your team, what Dante said is perfect advice. Listen to him
I’ve got a few more tips for you and others reading this to back up what @Dante2377 said;
Ignore your pretty 5* heroes for now. Level a 3*/4* team before you touch any of your 5*. Even if the hero isn’t top tier, they max quicker and cheaper (very important for developing bases). The quicker they level the sooner you can complete all of the rare quests, complete the challenge events, and fight stronger Titans which all give you ascension items that you will need. Most people hit this wall and get frustrated as their 5* sits there underleveled and underpowered (They don’t come into their power until after 3rd/4th ascension and you can’t complete any of the challenge events with these underleveled 5*)
I hope this guides you to a more fun gaming experience!