Have you thought about creating info products? Affiliate marketing is tough, takes a perfect mix of traffic and competition, or a ton of traffic. We have done it in the past, but its not our favorite way. Amazon is good for small income, but if you really wanna make money selling info products is the way to go. It sounds like you have a good start, maybe you just need a different direction 🙂
The best way to make money as a kid is to just start. Choose an easy idea and get to work. Get your first customers from people you know like family, friends, and neighbors. Over-deliver on your product or service and ask for referrals. Make a business plan to grow your business. Look for other opportunities for your next business. Look through these 200+ ideas to find more ways to make money as a kid or teen.
Music may perform better than books and other products, mainly because you can listen to the clips of an entire album in roughly 10 minutes and get a good enough feel for it without buying it to write a short review. If you have another topic that you're passionate about, great, but make sure you have a unique angle on the topic. People can get reviews about a lot of those consumer products anywhere. You need to give them a reason to visit your site.
In your parent's day, the only way to make a living drawing comics was to get your comics into the newspaper or work for DC and Marvel. Today, you can draw comics about anything you want and start your own site to host them with a little money borrowed from mom and dad. Selling t-shirts and space for advertisers is a great way to earn a little money with your own comic.