Personally I have found gentlemen stacked in my own college(s) to be far more effective at gaining tech than trying to steal it, at least until they get some experience and traits. Trying to steal a tech from a large country may likely get him assasinated, so send one over to westphelia and every now and again to try to pick something off. Don't steal from france to early because all your agents will die mysteriously. Once you do decide to steal go all out....send every agent nearby to a powerhouse school and try to steal 6 things at once for a few turns. Also, try some duels out, your agents will get duel-related traits, get them experienced on the agents of peon countries then start hitting the school of your enemy...and no, dave, you can't duel catholic priests or imams

the ones i have on permanent steal duty are the ones who spawn in odd places, like cycon, where i have no school, and i dont feel like loading them on a boat and taking them home

Remember, you get a research project for each college, so try to build a school in your newly conquered lands if you are going to have a large garrison there anyway. I also tend to build a church to convert for a few turns and get a missionary, then i destroy it and make a school

get the first 3 philosophies first to up your research rate, but pick wisely after that and dont take the philosophy ones too fast because each one increases unrest. I like the tree on the right that gives division of labor and joint stock companies, those dont increase unrest per se, but the buildings they unlock do.