My best games at demigod have been when I have built the GL, used 0 science and saving money till republic govt is learnt and installed. Then I check which techs have been giving to the scientific civs at start of 2nd age, trigger a GA and research a separate tech line at 100% science funded by tech sales gained from the GL to lessor civs. The GA combined with libraries built prior to the 2nd age or rushed at that point allows me to beat thew AI civs to the tech I choose, allowing me to sell it at a good price to the tech leadersfor high GPT or cash only, I do not need to trade for techs they learn as GL gives them to me. Their learning immediately slows down as they reduce their science rate to pay me and by the time my GA ends I have gained a solid tech lead which with appropiate deals pays for many rushed building and units and the strongest civ economically.