Need some help

Hi! I'm a long time AoE2 player, but played the game mostly in LANs casually with my friends years ago. Last week I've got the AoE2:DE and I'm trying to learn the game in depth. I find a lot of resources about early game and what you need to do in dark/fedal age, but once I get past this, I get a little lost.

At this point there is 2 things that I need to know:

-How to decide which upgrades should I do and when should I do? Beside economics upgrades, should I focus on university or blacksmith?

-How many villagers should I assign to gold and stone?

Thank you and sorry for my bad english.