I used to mess up on my sister's Yamaha keyboard, then when I turned 12 I started guitar. I also learned a bit of theory, but I guess exploring chiptune also gave me a lot of knowledge I didn't have before!
I'd recommend you to search on the internet to learn things like scales, it's all about the scales! Then you'll learn easily by yourself things like arpeggios and using octaves or stuff like that, LSDJ is really intuitive when you experiment with it.