As for what should your sandbox be, you have a few options. The easiest is to start a blog. That’s what this site was started as: a sandbox for learning content marketing, and it only became my full-time job on accident. A blog is a perfect sandbox for learning digital marketing since you can test almost all of the tactics on it, it’s low-cost, and you’ll improve your writing in the process.
In addition, you must know how much you want to earn by joining affiliate programs. Will it be your main source of income or just an additional one? For the first scenario, you should consider promoting products that are expensive and, consequently, that can bring you a good profit. If you plan on the second scenario, you can opt for affiliate programs that pay for sign ups or affiliate programs that pay daily.