Doba is a good drop shipping service and easy to integrate with eBay, but it is expensive. Not only does it cost from $49.95/month, drop shipping also requires you to pay a small fee on top of the wholesale cost of the product to cover the drop shipper's time spent packaging and posting the item. This additional cost can make significant inroads into your profit margins and it is not always the best way to make money in the long term - That's not to say that drop shipping is a bad idea altogether. It is a simple way to start a business, and in the long term, having some of your inventory drop shipped allows you to offer a broader range of items to your customers without the risk of holding stock.
All the best!