I found that in Single Player Games (I play Deity), Marco Polo's Embassy is more useful than the Great Library. You can trade the techs you really need, you can trade maps. My own research focusses on key technologies which allow to build the correspondant wonders.
When i trade techs, I begin with the civ that owns the GL.
I don't want to be the #1 civ in the world, i normally give a lot of techs to my allies to make them #1 and #2 civ.
without GL or MP, it's harder to win, but it isn't impossible. You need ships and diplos to contact the other civs (embassies).
Later in the game you should build the UN.