The faster you can become a professional illustrator the better. I’m going to tell you what you need to be spending your time on to become a professional, faster. More importantly, I’ll tell you what you shouldn’t be spending your time on.
You could spend three months working very hard on the wrong things, reach the end and still not have a paying client. Using your time effectively is hugely important at the start of your illustration career.
You can also read this article on the subject: What not to do
Getting an outside perspective on your portfolio can vastly improve your work. By seeking out the opinion of someone in the industry, you can get a fresh pair of eyes on your work and they can often see what you can’t.