If you have graphic design skills then you could make money online by creating and selling your own design elements, like templates, fonts, graphics, and other assets. This is a great way to earn extra money, and build up a portfolio of work, which could lead to you picking up freelance graphic design jobs. Websites like Envato Elements pay you a fee per element sold, which can become quite profitable if your work is popular.
Ebay is a bellwether. It's been around since nearly the start of the online boom. But, like any other platform, success can seem fleeting if you don't know what you're doing. Selling items on eBay, professionally that is, can be an art form. Getting people interested in your auctions isn't always easy, especially when there's hefty competition and low demand for what you're selling.
Etsy: While Etsy's popularity has declined recently, it's still a great resource for selling handmade items online. No need for complex ecommerce sites or merchant accounts or any sort of automation. The company takes a commission of every sale and charges a small listing fee per item. But many still use Etsy as their primary source of income. The best part is that you can also sell digital products on here such as poster designs.