That is really awesome if you are drawing on your iphone. I find the screen too small to draw anything significant. Making vectors is good because you can do them with a mouse, but having a tablet makes it slightly easier and faster to do.
I couldn't do my drawings at first. I took some time to learn the program so that I could do the drawings. You won't get it right away but with some patients, practice and a good snack, you can do it. I actually made it in adobe Illustrator.