Originally Posted by
Fynn
Yeah, generally what Hypo said. If you keep fusing, you should be just fine.
Also, keep the arcana in mind. Each Persona is assigned to a major arcana of the tarot. And each social link represents one of those as well. Now, these are mutually relevant. The higher rank your social link of a specific arcana is, the more exp. the newly fused persona gets at the beginning (that's the only way to fuse personae above your level). In turn, if you have a persona of a specific arcana with you when you do the social link conversation with that arcana, you get more of those invisible points than usual and the next rank-up will come faster.
Glad you're enjoying the battles! That should kind of ease the tedium of Tartarus. Just don't get discouraged and know that if you ever want to play P4, the dungeons are done much, much better.
Also, Junpei is the single best character in video gaming history. Just for the record.