On Deity I feel the GL is at its strongest.
I tend to start off with a small ICS territory them find a neigbor , hook up to iron or horses, get enough tech for horsemen or swordsmen, build a military for a few turns then go on the rampage. I keep their cities , and depending on the next nearest neigbor I might go through them too. My tiny ICS towns just build a barracks them units, thats it. One town ( possibly capital, often not as I plan to move the capital) will be designated to develop. Tax is 100%, unless I feel 10 % luxuries will make me more efficient, and I only try to trade or bully for techs that lead to literature, contacts and world maps. I try to time literature and a palace prebuild to get the GL soon afterwards, and often get 10 + techs the next turnd from other civs. The whole point is not to pay anything for techs I'll soon get for free anyway, and can't utilise as I'm busy building units everywhere.
I stay on 100% tax until Literature is gifted to me, then I often find I can buy the next 5 - 10 techs in the middle ages with the huge cash pile I've built. As I do no research I need no librarys and universities, leaving me free to concentrate onthe other city improvements. This does leave me behind in culture, so I tend to build colusseums even if the town doesn't strictly need them. Clearly at some point I have to join the SCience race , but I generally leave this until after Industiralisation so that its a quick build of library then Uni , then move the slider.
Robin