About those minors civs, I advice to get research treaty with all off them ASAP (one way treaty, keep your for major civs). I advice to do the same with all major civs, if possible. A good way to get this treaty is to trade for a bunch of low tech/unique tech you may have, adding some obsolete ships you may have if needed.
And when you get techs (and r&d trade good) who improves the global r&d effiency, trade it (for cash, ships, or whatever) to all AI's (minor and major) that have their r&d treaty with you. It will helps improve your own R&D on the long run, plus giving the AI the oppportunity to discover faster those techs you couldn't discover yourself (ie tradable racial techs).
Do the same with econ treaties with minors (it is harder to get one way econ treaty with majors, especially those who are ahead economically, but not impossible if you are willing to share almost all your current knowledge) when it is possible to get them (usually after one year-one year and a half on larger maps). As for r&d treaties, don't be affraid to trade to them techs with an econ bonus (ie xeno economy), since it will affect you on the long run too. But don't trade them new forms of governements for their econ bonus (republic, democracy and federation), since it will also give them the diplo and influence bonus sticked to those techs.
Getting those "one-sided" R&D and econ treaties with minors is pretty easy, even on harder levels (I play on masoschistic), could be a bit expensive with majors (then go for some diplo techs if you lack diplo skill, it eases a lot), but always worth it, since you litterally "hold'em by the balls"
because any current treaty can't be broken without any war declaration, and since it isn't you who signed the treaty, you don't get any penality if you war dec' them, but they will if they war dec' you (see below, next §). I like this strategy since it can help you having only a small military since even if they hate you, they won't attack you too early, keeping your hard earned cash for your own econ growth, not diverting it on early warship maintenance.
Keep your own R&D and econ treaty for majors you want to be friend with or to help getting an econ treaty with some powerful major, and don't give your treaty to a civ you're gonna attack, you'll get a instant and permanent negative diplo modifier with ALL civs once you war dec the civ you gave your treaty: "They don't trust you" wich is pretty painful in example if you're heading toward diplomatic victory...
