Hey, i found a good tip for new starter. As first you need to save up good amount of purple gems (6-7k atleass) then you switch between 2 gyms, they will offer you Super bonus which will have 1 of the best offer is to double the amount of your sweat drops, if it's not it then leave it - go for the other gym to reset it. You will have a really nice drops to upgrade your gym.