Know your prices
Look for the price of the item at your local art supply store, or online. (I find it easiest to do a Google Search for what I am looking for then selecting “images”. Much quicker to see from photos.) Once you know the best price you can get the item for you know that when you look on eBay that you are getting a good deal.
Buy locally and look for Free Shipping.
The shipping fee can make the price more expensive than buying from an art shop. Look for auctions located in your own country to avoid paying extra amounts for shipping and customs fees.
Reputation of Seller
Pay attention to the Ebay sellers reputation, which shows how much they can be trusted. Look at the comments left from other buyers who have purchased from them before.
See what Art Supplies you can buy on eBay: