If you have an affinity towards racing games (yes I'm aware this game's racing mechanics aren't exactly well-developed), you can get an easy 20 tokens in roughly 2 minutes.
If you have a MechroMancer with Close Enough 5/5 & The Bee (or a crapton of Anarchy Stacks), you can get 25+ tokens in 1~2 minutes (depending on your luck with spawn patterns of the SuperBadass's you need to kill).
The arena fight is easy enough, but I don't feel it time-efficient for gather tokens as fast as possible.
red_ghost from Monster Hunter / Phantasy Star Universe