I'm a relatively new player. Only a couple of days have passed since I first started. Only recently have I learned that I wasn't supposed to be using silver units for combinations. I've used almost all of the silver units that I'm not currently using as level fodder. I've received all of the completion rewards through Tower Overwatch, and all of the strategy lesson bonuses as well. Should I start over? I wouldn't be able to receive the reward for the Feng Shui event, I fear, and I already spent a small sum of money on the game.