I start to buy about November.
I can't get my head around it any sooner.
It just makes me feel I am myself, becoming a drone.
I shop in 5 different ways.
e.g. ebay or store...or yes even the odd garage sale, with somethings brand new!
I buy things when I see them. Sometimes that means having Christmas presents ready shortly after the last Christmas just ended, but it also means I usually end up buying more presents, because I find things nearer to the time as well.