I studied Illustration, but the graphic programs I use are pretty easy to use (mainly Illustrator and indesign), and I just taught myself over the years.
There are some simple tutorials online. I don't think you need to go to college to learn them to be honest, just have a play with them and work it all out. 
For clipart I usually make those in photoshop and save as high resolution PNG files. I basically look at what themes are trending then draw some cute images (bundles sell best).
It's clipart so it doesn't have to be amazing and people still buy it (one of my best sellers is a cactus!). As long as you are happy to license your work - go for it! 