How do people complete sets?

Just dipping back into the hobby with my son turning 9. He only cares about chasing inserts but I'm enjoying working on the set, so my question is: how does everyone complete sets, especially for cheaper issues like Topps S1?

We've opened 2 boxes, participated in a few breaks and bought a few loose packs. I'm about 60% done with my set, how do other people complete theirs?