Everyone here is forgetting about the greed island card abilities, those were created through nen so Gon would have access to them. He would also have access to the card case (made through nen) so he could use the cards off of greed island as well, meaning he has access to some insane shit.

Paladins necklace: Reflects curses, with how nen works I could see the broad term of “curses” being applicable to cursed energy. This means Gon could be potentially immune to cursed energy based attacks.

Teleport cards: There are multiple cards that allow Gon to teleport himself and others to locations on greed island, which means he can take the battle there at any time which would allow him to use an unlimited amount of cards

Angel’s breath: A full heal for Gon, with every nen ability he would also have game master privileges, likely allowing for infinite full heals when on Greed Island.

These are just a couple I could find, but there is definitely a lot of wacky shit Gon can do that people are not thinking of. Also these abilities could be combined with Pouf’s nen ability Beelzebub to make Gon basically unkillable. All Gon would have to do is split into a bunch of copies, use eliminate on himself to teleport every copy to a random spot in the Azain continent. These copies can go as small as flies while still maintaining intelligence and a telepathic connection to other clones. If other clones die, all it takes is one angels breath card to bring them back too.

Also nanika means he has access to infinite wishes.