Hi Loren and welcome to the forum,
Depending on the product, it can be extremely difficult to compete on a platform like eBay using a dropshi business model. The problem you have is that you are not just competing with other dropshippers selling the same products, but you are also competing against wholesaler's as well as some manufacturers using the platofrm as a direct sales channel. Throw in people using certain marketing techniques like loss leaders (which is selling the product at cost or below), and you can see what sort of brick wall you can come up against.
The biggest mistake that new dropship sellers make in this industry is try to compete in hot markets. Of course everyone can understand the lure of wanting to sell the hottest and most popular selling products, but you need the right tools to compete in those markets because that's where the competition for sales is always strongest.
For dropshipping, we always suggest moving out towards the edges or what are typically called "niche" markets when dealing on platofrms like an eBay or an Amazon. Niche markets can take quite a lot of market research to discover and many people simply stumble upon them. These are markets where sales aren't fantastic, hence the competition is much lower and the dropshipping business model can be more effective whe dealing on super competitive platforms like an eBay or an Amazon.
That said, a markeing technique I am a big fan of is bundling. If done correctly, this option can open up sales in the more competive markets when dropshipping. You can read more about this technique here: Link hidden: Login to view