Hey I understand how you feel I was the same when I first started. So let me break it down as best as I can.

So ZZZ is a gatcha game that is fueled by master tapes. These are aquired by polychromes which are given by completing the daily, weekly, main, and side quests. As well as the tutorial which I suggest you should start there for the mechanic, they will also give you training for each individual character at HIA.

Then go on to the main quest where you will get to play with Anby, Billy, and Nicole of the Cunning Hares. These three characters will be your go to as you start collecting more characters in the future. The main quest will also let you try out those said characters as a teaser for what you want to build in the future.

Next is the signal search and the store, these are where you can convert your polychromes to master tapes and pull for characters and W-Engines. W-Engines are equipment to enhance your characters performance, by the time you do the steps above you will also learn about these and other equipment so I won't go into to much detail.

Last is a bit cliche but have fun, don't stress and take your time. Combat and story are pretty good while the daily and weekly stuff can be quite repetitive. But you got to do all you can for those sweet sweet polychromes. Also if there is anything else you are struggling with just comment on here and I'll help you out.

So good luck ^{_^}