Call me a hedonist, but I usually start with the most fun stuff that gets me some result soon (usually the part I already am good at). Then ideas come for the rest, the dark days I certainly procrastinate until I feel guilty enough to go on again. Works for me.

It helps a lot if you have an employer that gives you the time. There is no substitute for getting paid 8hrs a day to learn new difficult tasks.

It's actually the reason why some of my self-employed friends got a regular job again.