I don't usually start wars until the Medival or Renaissance Eras and i use Serfdom instead of Slavery because i prefer faster workers.You might want to consider researching bronze working earlier. I find if I dont research it fairly early it severly limits my game. With bronze you can chop forests, enable slavery to keep population in check and reveal copper which is necessary if you're going to start an early war.
Bronze Working for copper, Axemen, slavery, and chopping. It's probably the single most powerful tech in the game
You said that it is because it gets money but if you get the wonder for a religion you can spy on enemy cities and get money...........
guys, getting early religions is fun, but its not efficient. maybe hinduism or buddhism if you start with mysticism, but other than that, you're much better off researching something else.
bronze working is obviously a top priority for the numerous reasons already mentioned.