I have no niche, LITERALLY.
The strategy I use Id called something like "Sell whats selling already" approach, just finding succesful Dropshippers doing exactly the same thing I do.
1. "Find Item on Walmart/Amazon/HD/[Insert whatever US Supplier that has online store here]"
2. Go ahead and list it on your eBay store with a % markup (Take eBay/Paypal Fees into account here, is arround 14% as general rule if you are US Based)
3. Put a competitive price (Try to list item at same price as your competitor or lower!)
If you are interested in these particular method im telling you, it works, and I learned all of this without paying for education, I just lurked arround every single place possible that had eBay Dropshipping related stuff and started going on a spree reading everything I could and taking action.
It works, for what is worth

!
PS: January is a good month to start learning since christmas just happened and sales are so low that you are not 'missing out in any crazy holiday' right now lol..