Ski Essentials Where Is The Best Place To Buy Ski Equipment From And Also What Are The Essential Items - Other Than Obvious!?

Where is the best place to buy ski equipment from and also what are the essential items - other than obvious!? - ski essentials

My son is skiing with the school on average in February and is a rookie. Can anyone recommend places to buy ski equipment - and even children as a brand name - for skiing are essential.
Although there are many questions, what is needed - advice in this department will be greatly appreciated.
Thanks