Semi new player help!

Hi! I’m a semi new player and I’m just very confused on how to power up in the game! I’m just stuck at this certain power level that I can’t seem to get past, and I can’t even play the story because I’m just to weak! I don’t know if it’s because I’m focusing on trying to upgrade my SSRS? Or what! I just can’t understand if anyone has a detailed video or even a good explanation or can give tips and tricks I would really appreciate it! And before we comment I already know about potential but it’s such a hassle to grind! Unless I’m missing a hidden secret about getting potential a little faster than usual, and I’ve also tried to level up but i seem to be capped at level 30 for all my character I don’t know how to raise the level cap, I’m just really confused and lost at this point of the game.