If you have super knife, go to Spy Hunt, and keep killing people, but don't become super spy, let someone else be it. When someone is superspy, just superknife them and you'll end up with like 400 EXP and 700 GP in like 7 minutes.
Grab some friends and do Spy Hunt as long as you can
Try to do it in servers that have a GP + XP bonus
like Delta - Echo - Kilo
Not Alpha or Madness, try to stay away from those Non XP+GP% servers.
Then from there play without a super spy
Kill each other for like 8,12,16 minutes etc;.
In the end, you should have 400=1200 xp or GP (each) without super Spy