In VV2, I prefer to start in buying the level 2 of Engineering and to build the dam as soon as I can.
Then I buy the level 2 of Science to get the tech points faster.
After that I purchase the level 2 of Exploration to have the cauldron and the stews, that may help my workers to stay in good health and, as soon as I can, I may put some villagers on cutting away the thorns and so they improve their building skills.
And I buy the level 2 of medicine because I want not to see my villagers becoming elderly too early.