Celebrity agents have nothing to do with how much money you get for concerts. What concerts are you talking about specifically? You mean the ones for your career as a rock star?
The thing that usually allows people to make more money when playing for tips is the number of performances you have for songs. There are some songs that are broken when played on an electric guitar that means they stop playing after the first few notes. Or you could use a normal guitar and cancel the song after it starts. Doing this will increase the money made by a lot.
Celebrity agents have nothing to do with getting concerts or party invites. They are only there for very specific opportunities: the restaurant, work out for 4 hours, befriend so-n-so, have a drink, go dancing, cameos in film/plays. Since celebrity opportunities have nothing to do with guitar, that means any talk of them is actually off-topic.