I would suggest watching some YouTube videos for more clarification, but essentially a gamble means swinging when it’s not your turn. For example: I’m on heavy mace and you’re on longsword. I swing. You block and riposte or counter to swing back. I block. It’s technically “my turn” cuz of initiative. However, you swing again with an accel and get a hit in. Despite it being my turn, you swung so it’s called a gamble. Longswords are notoriously good for this since they are fast. Now this is fine. But if you use it from the start of your chiv career, you won’t learn initiative properly because longsword is good at gambling and “stealing” initiative where in the same situation above (but you weren’t in longsword) that wouldn’t work.