I learned to estimate using T&M calculations. It was pump and tank work so I had to figure the size of the hole for the tanks, the number of loads to be hauled out, the backfill required, ditches, piping, conduit, x-proof fittings, wire, etc etc etc. Then how long it will take to do each task. Every job was a little different layout and there were no package estimating programs for this.
Then I went out on my own and stayed with this kind of work, so I just kept doing it in the spreadsheet I had set up.
It seems to me that if you are doing bigger jobs, then those estimating packages are probably worth it. If you have never used one there will be time invested in learning it.
So my question to you is, what kind of work are you going to do? Does it lend itself to these estimating packages? Mine didn't.
If you are just trying to stay busy working for yourself, I'd start off building your own spreadsheet. If you don't understand how to recover overhead and what the true cost of being in business is then you should definitely read books. Others that have better experiences should chime in.