I think Arsenal would be the best choice for him. First of all, Arsenal have the money, and they can really sign him and offer him a good salary. Chelsea also have the money, but I see that, lately, they have been acting more reasonably with their transfers. Arsenal are an ambitious team, although they are always missing something to win titles. Chelsea are doing even worse at the moment.
Another option he is considering is Juventus, but I am not sure how ready they will be to fight for the Scudetto this season. It would actually be good for him to either return to Napoli, because those guys are dominating right now and will play in the Champions League, or move to Arsenal, because at Galatasaray he does not have many prospects.
His high salary will also be an obstacle for Arsenal and I am sure they will take another approach that is far more profitable.
When talking about money problems, Manchester United and Chelsea are far better than Arsenal so that the player's potential moves to Arsenal with an assumption like this very small.
But there is one advantage that Arsenal might offer because they look more convincing to help Osimhen achieve his best career because in the last three seasons Arsenal have always been able to finish in both standings.
In Galatasaray itself the future is also unclear because Osimhen has ambitions to play at a much better club.
Returning to Napoli is also not a solution because he might never be accepted by fans because of the speculation that occurred with him while there.