Problem with climbing

On recent robocup, Me and team was on competition. We had robot that had rubber tracks, but it wasn’t able to climb up hills. We was trying to make wheeled robot, it had 2 front wheels and behind was thing with small ball that can roll in any direction. But thing was, robot wasn’t able to climb up anyway, because its weight came to rear ball wheel, and fell down (because that one has no traction).

So my question is:
Which wheels or tracks has best or good traction? And how to implement it to robot?
Thanks for all answers

this is a problem most teams have including our own. But sometimes the problem is not purely the traction it could simply be because your motors are not strong enough I recommend looking up the motor you are using and its torque to see if the are strong enough to climb up hills.
other than that to improve traction you can use wider wheels
some wheels have very smooth surface so using something like a sand paper you might be able to make it less smooth and increase the traction.

All the best