CUC - margarita snails, cerith snails, nassarius snails, astrea snails, blue leg hermits, scarlet hermits. Those are the basics.
I would not suggest adding 3 or 4 clowns to the tank. You will end up with only to in the end most likely. A pair of clowns is all you need.
I would not add the cuc until you have all the rock in the tank and have tested your parameters for at least another week. When you get 0 ammonia and 0 nitrite and see the nitrate spike it will be time for a large PWC
The brown algae looks like diatoms to me and are perfectly normal at this stage.