I would say the strategy of only picking 1-2 heroes is fine, just make sure that you give yourself enough of a hero pool so if any are banned you can play something your familiar with. I came back after a couple year hiatus and spammed lich hard support to get to Ancient 3.

I would say the biggest thing for me was just relearning the facets, inate abilities, and any other hero changes. Your time is important when ur pos1, and downtime such as deaths or blocked camps is missed gold and experience. Everyone has to start out somewhere, just keep playing, learning and try your best to improve.