Here are some recommendations:
1-After the guy mentions his level in COD add a pannel of awkward silence between both characters. Those beats can help to solidify the punchline because the awkward silence makes it look like the guy is gonna get rejected.
2-Another one is for the guy saying in an overconfident manner that he is level 70 in COD.
3-Exagerate the positive reaction of the guy recluiting the level 70 COD player.
4- This can be another angle of the joke If you wanna be a bit more subversive in the punchline you can get the guy rejected, for something related to COD, like "level 70 is for noobs" or for "we dont accept f*cking campers".