I just XP farmed the hell out of the below and got to level 12 with all my party before taking on Kamoshida. You'll need to pay attention to fusion later down the line when you start raking in more personas. Essentially, it's combining different variety of personas to get your a newer one which has allows some combination traits and some new ones. They will give you more skills to play around with, so keep experimenting with them to form powerful ones. At the start, it's fine to just go with the normal ones that you gain along the journey. Whatever you do, DO NOT use the DLC personas, they are crazy overpowered and broken. This game offers a very deep combat mechanic if players choose to explore to the very end and it's very rewarding.