For anyone new starting out I would advise them to do a proper analysis on the logistics involved with selling the products they are choosing to focus on before they actually begin selling. It is easy to fall into the comfort zone of selling a product you are familiar with and not actually analyze if it is something that makes sense to sell online. Product knowledge is important but it is a smaller part of the ecommerce equation these days. Look at your logistics model and how that relates to eBay's algorithm which prioritizes listings with faster deliverability. Customers want product that is readily available, is fairly priced, and can reach them in a short period of time. Ebay is entirely geared to pairing those customers with sellers who can meet their needs.
Look very carefully at the average selling prices in your category and what the typical shipping rates are for the product. Ensure that all of your shipping prices are setup where possible to show regionalized rates. If you use flat rate shipping without thinking things through you may be grossly overcharging shipping for some of the most populous markets for the benefit of lowering shipping costs for the least populous markets.
Think about your logistics costs as a percentage of the cost of the item you are selling. If you are looking at selling products with a low average selling price and a relatively high shipping cost then reconsider. If you are choosing an established category then understand that how fast you can get product to a customer is going to play a large role in your success even if you have a competitive product and shipping price. If you are fortunate enough to be located near the border, look into international package forwarding services that can reduce your shipping costs and increase delivery speed for your international sales.
Unless you have exclusivity, an advantage on availability or pricing, or you are competing in a category with little competition the above is critical to actually growing your sales. Don't invest in inventory before you have this nailed down. When you do invest in inventory, look at how quickly you are turning that inventory over rather than just your sales revenue. Be willing to be honest about geographical limitations that may impact your logistics costs and consider alternate products that are better suited to those limitations, even if they are way outside of your wheelhouse. You can learn a new product category but you are not going to reinvent the shipping industry.
