When buying on ebay there are some important steps to consider and I will give you seven of the check list that I have found to help me get the best deal for the best price.
1/ Decide what you want to buy (ie) stamps try to keep it to one or two lines of stamps , you find that you will buy a lot of stamps you dont want if you dont.
2/ Decide how much you want to pay and stick to it , Ebay is such a good tool for buying that if the item goes over your decided price then there will always be another item or similar come up later.
3/ Always look at postage, this can vary greatly and will make an item quite expensive if you don't factor this into your purchase price.
4/ Watch what currency the item is quoted in if not in Aussie dollars then you need to look at the exchange rate to see the actual price you will pay for the item also check the postage if it is not in Aussie dollars then the item can be a lot more expensive than you want to pay for it .
5/ Try to develop a list of your favorite sellers and go to their listings you will find that they will get to know you and trust you and you will get to know them and the lines that they carry.
6/ Always contact seller as soon as possible and let them know how you are going to pay for the item and be prompt in you payment.
7/ Always treat the seller as you would like them to treat you , they are not your enemy they are your supplier.
I have found these hints to help me in my purchases on ebay