Extra income ideas? (Jeddah)

I'm just looking for a general discussion/
I'm trying to figure out ways to have extra income here but I'm not sure what I can do. I've recently started teaching Arabic & English as second language.
I do have a full-time job, but like a lot of expats in Saudi we're usually underpaid. So I took my teaching skills in use and been teaching after work most of the week.
I'm mostly curious to see what ideas you guys could have on mind, seen people do, or at least think people should be doing.

For example, I signed up for mystery shopping and I absolutely have no idea how this stuff even works. -_-" I got accepted and all but I don't understand the procedure