Important Techs to get first

[KAZUY4]

Some techs probably are not that important at the beginning, because of lack of resources to take advantage like game etc... but some techs like Irrigation, this tech if you researched first, you will receive +1 pop to each city, Engineering: +1 production to each city, Literacy: +1 science to each city. Those are huge bonus, and to be honest, sometimes is easy to buy basic techs from the others civs. Also you can sell these techs to distant civs and get some good gold or simple extort other civ and get techs for free in exchange of peace.
Take some times and you can see how to get nice techs and then how the other civ react to that.

 

[donpost]

I always considered Irrigation important, because people = power in CivRev!

Industrialization is another good one: +5 science per city if you get there first, AND it unlocks factories.

I love the idea of extorting the AI for techs which you then sell on I'll definately give that a go in my next game!