HxHEnthusiast
He can befriend different tribes in the jura forest. also i think he some unique skill nothing overpowered but something that suits him. As for human.souls to get strong he should waitas much as he can, since the stronger he is normaly before evolving the stronger he gets after the power-up. Or just get souls when human nations fight each other. By deploying a barrier where they fight, that way free souls.
'See my other comment' (Sry is little Long) He doesn't need some Rimuru level OP unique Skill. But at least having one is a must. Average? Not really strong? Is OK, they exist. And the memory thing. It doesn't make him stronger. He just keeps his life and knows what's happening. Nothing special. Poeple like Tear, Footman and Laplace can all percieve Souls, even Clayman can. He can even live without his Body and posses a new one with some Soul traveling bs. That's what I mean he dead without mem'ries. Cause they are part of Spirit Body, which means, the others can see when they missing.