I feel your pain,
I also went on my own about five years ago. I know the trade but had no idea on how to do estimates.
I finally started bringing a notebook with me on big jobs, like a new house or remodel. At the end of each day I would write down what I did and how long it took. That's called job costing.
I now bid houses at approximately $3.00 per square foot. Depends on how extensive the electrical is. Recess cans make a big difference in price.
I don't buy any light fixtures except for the recess cans. I write that in my proposal. You have no idea what kind of light fixture the home owner wants and even if you bought exactly what they desired it would still be wrong. I Make the home owner or the general contractor buy the light fixtures and the ceiling fans. Your price looks lower and there are less headaches.