How easy to pick definitely depends on what lock you have. Most modern kwikset are actually very difficult to pick and require a different technique than a typical master lock.

Lpubelts has rankings for common locks so that you can buy progressively instead of guessing in the dark how hard a lock will be. Personally I think a master 141 then a master 150 is a great progression with dirt cheap locks.

The 141 is a little more precisely built than your no 3 so you can feel better going pin by pin. The 150 has really obvious security pins that are easy to feel to get started on security pin techniques.