Diablo 2 how do you gambe with gheed without getting ripped off?

You don't, that's why it's a gamble.

The gamble option is for players with far too much money, money that they'll never use, and since they have so much, other picked up gold might be wasted due to the stash storage cap. So the gamble option is something to spend all that money on, sure you might end up with trash, but there's a chance of getting a good item.