It's one of those pitfalls that a lot of newbies fall into, not getting the research right up front and getting burnt by costs such as eBay and PayPal. You really need to get all your costs worked out and then you will be in a better position to know if there is any margin in the products you are trying to sell by comparing your competition.
Bundling or package deals is a favourite topic of mine, especially for dropshipping. Getting a POD (Point Of Difference) is extremely difficult with dropshipping and package deals is one one you can get out in clean air.
So what you do is look for a product range, let's say jewellery. You find a nice necklace to list, so then the idea is to find products that compliment and accentuate that necklace, perhaps a matching bracelet or ear rings or even both, then you list them all as a package deal. The trick here is that you only make your margin on one item and the others are passed on at cost.
The idea being that it is going to be far cheaper to buy the set from you rather than buy the individual pieces from another supplier.
Now I've used jewellery as an example, but it can work with any market. Fishing, bundle rod, reel, like, tackle and so on. My suggestion is that you try different sized packages. Jewellery for example, try just necklace and ear rings in one deal, then add a bracelet to another deal and so on.
Give the customers a choice of package deals and then over a period of months, take a look at your sales data and you can then see what package deals need to be tweaked to get the most out of them and which ones are working well.