Consider bundling products that work well together.
For example, if you are drop shipping mobile phones, consider a package deal that included the phone, maybe the case, hands free kit....you get the idea.
You need to be using the one supplier fro all these products, but what you can do is leave off the margin on all the other products or at least most of them, then make your margin on the phone itself.
The trick is to provide better value for the customer by buying your package, other then they would get by buying the items individually.
You're not losing money by doing this as you are complementing the mobile phone with products at cost (remembering to factor in shipping)
You don't want to ad too much to a package deal as you might start have to price it out of some buyers reach, you just want to find that medium ground where you can offer a unique package at a price point where buyers see true value.