Re: Where to start?
Keyword = Research
Look at the types of things that you wish to sell, if you are only looking at selling on ebay, search them, see how they are selling, what the listings are like, how well they sell (you can use advanced search to search completed listings), see how much they are selling for, if you do not use an auction template get one, it makes you stand out and look more professional.
Regarding the supplier, look at what you can get at what price, see if you can make a profit on it from ebay (though there are other means of selling such as your own site). Make sure that it is a reputable seller that you are buying from (there are certain things which you should be wary of stated in multiple threads on this site), if you are unsure of a wholesaler start a topic and ask if anyone else has dealt with them or has an opinion (and btw, many sellers on this forum are wholesalers).