Hand 2 when you hit the set on the flop. BET SIZING IS KEY. You realize that you bet 1/3 the pot OOP vs 4 people (including SB obv)? That is not a good board for your hand, too many draws. Bet AT LEAST 20 cents there, I would say even go for full pot. If they all fold, who cares? You are going to make them pay for their draws, not give them incredible odds. (The first guy who called was getting 4:1, next 5:1, next 6:1, etc) You do not want to be giving such cheap cards when there are that many people and draws. If it were a relatively dry board it wouldn't be a problem. Learn to recognize what boards are good for your hands. You're lucky the boat hit on the river.

Keep grinding away and putting in the volume and you will be fine.