Play 6.h4 g4 7.Ng5, this is a little like the Hamppe-Allgaier Gambit (1.e4 e5 2.Nc3 Nc6 3.f4 exf4 4.Nf3 g5 5.h4 g4 6.Ng5), but in a much better form for white due to the extra development tempo and the fact that ...h7-h6 doesn't force a piece sacrifice. You can also look at the Allgaier Gambit for ideas (1.e4 e5 2.f4 exf4 3.Nf3 g5 4.h4 g4 5.Ng5).
I can't find anything on what to do when pawn to g5 after knight to f3. I'm assuming that it's because it's a really stupid move (I think), but I never found a way to punish it, it's probably the most popular response that I've gotten in the Vienna Gambit. Help me find a way to punish this move.