Farming first - most definately!!!!!
Up to Level 3 as soon as you can.
Else your village will starve.

After that Level 2 of everything else, I usually go for construction next then the rest as I feel the need for them.

Getting to Level 3 on the rest takes some time since the tech point levels are pretty high. But you will need Level 3 in everything to complete all your puzzles for the game.

Everyone has their own strategies tho, but most of us do agree on the farming. A happy villager is one that isnt hungry.