If it's just for daily art than I get supplies from dollar stores, yard sales and clearance items at Target, Walmart and Micheals. I stock up on markers, crayons, glue whenever they go on sale. Usually Target in the States has the best clearance/sale prices at the end of summer. I have had a fair bit donated to me as well from friends and families.

If it's for a gift or the odd craft than I get items at Walmart, Micheals or whatever store carries what I need.