I'd go for Economics. You can get it in 7 turns, and you can often beat the AI to it. I think they are researching Democracy at the moment. Use Economics to get luxuries from the Iroquis, along with Astronomy. Hopefully this will allow you to sell all the goodies you have. Get other techs from other civs.
You could use some more Aqueducts, especially in cities that aren't completely corrupt.