While many people still use eBay and sneaker forums, social media is great for two reasons to sell footwear: There are millions of active daily users, and it's completely free. Those two aspects alone make it the perfect place to make some money selling your sneakers without additional fees cutting into your profit margin.
Take a look at the kicks you're selling and think about where they will sell most easily. The retro Jordans from last Saturday will probably sit in oversaturated marketplaces like eBay. A Facebook buying and selling group or a simple Instagram post might be a better alternative. Consider this before you spend precious time listing one pair of shoes on seven different platforms. It will save you time, and that's just as important as money.