i think we're all over looking the hovercraft... (
)
For a really tight budget, that would probably rule out crab, mecanum, or omni (spending money on wheels and the drivetrain might not be most well spend, depending on the game)
Probably one of the easiest (and cheapest) to impliment would be the 2 wheel / skid plates.
!*caution*! with the gyro, make sure its rated to a high rotation, when we tried to use that with our robot this year, it messed up because it could only do 80 degrees/sec !/*caution*/!
I would say experiment as much as you can in the off-season, build a generic frame, and try different configurations with the wheels, OR browse soap's collection of matches, and take a peak at each of the videos.