Hi Girts Kalns,
With electronics being so in-demand in the buy/sell industry, you may just be flooded with large scale competition. Not to discourage you or anything, but you can get around with competition by selling at your own online store. That way, you wouldn't have to compete on price wars with large sellers from popular online selling sites such as eBay. Just remember, to gain traffic to your site, make sure you use the right keywords when listing your items.
You can checkout SaleHoo's Market Research Labs (once you become a full member) to find out what's currently hot in the Electronics/Gadgets category:
https://www.salehoo.com/labs .
Just a tip: Normally, consumers purchase high end electronic brands for known quality reasons. Try looking for a supplier selling selling generic brands with similar qualities (there are a lot out there, you'll be surprised!). The best way to sell these items is to highlight their best qualities, comparing it with a known high end brand.