I have a different idea on pricing for new developers: decide what you want to really get paid (hourly rate) and if you need to "eat" some time learning, then eat it. You'll get faster as you learn more and hone your process and eventually won't need to eat any time. Much easier than raising your rates with existing clients later.

Also, find ways to reduce the amount of time you spend on non-billable tasks (time tracking, invoicing, etc.)