In regards to dealing with genuine wholesalers, the most important thing to do is discuss your purchasing requirements with them. Most wholesalers will have what is called an MOQ (Minimum Order Quantity) that you will have to meet. However, if that is too high for you then by discussing your requirements, you may find some can me a little more flexible.
That really is the key when trying to do business with a wholesaler, find our their requirements and discuss yours with them and see if you can come to terms on doing business with them. Just remember, the general rule with wholesale is the more the purchase of an item, the less you pay per item.