My worst decision was playing in bustabit.com site and then playing in dice game and losing most of the coins, after that i found one of the script in bustabit and recovered the lost bitcoin, and now only doing sports betting as i have some knowledge about cricket and by following my instinct i have made a good profit.
Hey friend 90% of us have made the same mistake but the bright point for you is that you realized that gambling is wrong and if you see in gambling section there are most people who still gamble and they will regret later 
. My worst I can not choose since I made terrible ones.As a newbie I lost many times in gambling in the past, every time I used to feel that this time I will win it big and recover the past losses, but unfortunately that day never came and I kept on loosing more and more.