I'm going to be the oldie who swans in here to remind you not to take the physical health of things like your eyes, neck and wrist for granted. No, don't draw on a phone. Definitely don't try to draw a whole webcomic on a phone! It's probably the least ergonomic thing you could choose, and even a very young person could wind up with neck and hand cramps from that. 
If you told your parents you were saving for an iPad/Apple Pencil because you like to draw and want to make more art with it, I'm sure they'd understand. Many people have some form of creative outlet, it's completely normal. Just tell them yours is drawing, and show them some examples of art made in Procreate to demonstrate why it's more versatile than pencil and paper.
The learning curve for Procreate is very small. It feels very natural, and is enormously intuitive. There are heaps of tutorials. And because you're drawing directly onto the iPad screen, there's less of a learning curve than there is for a tablet!
I'd definitely recommend the iPad + Apple Pencil option! It's also a great personal device which is good for so many more things than just drawing on. It's a wonderful piece of tech.