Justin has metal casting - that's nice. Less reason to research it yourself. AI's like to tech the bottom part of the tech tree.... they'll go for Monarchy, Iron Working, and Metal Casting, and Machinery before other things. Once someone else has Metal Casting as well, there's a good chance you can trade for it. Also, if you get short on cash, look for cities to put hammers into wonders that you have the bonus resource for. You can do this with oracle - if you intentionally delay building oracle for a couple of turns to get civil service in, have some other city put hammers into Oracle while you wait. [You have to fiddle around in the production queue, to do it]. It'll turn those hammers into gold quite efficiently. Similar with any stone wonders that crop up. Given your traits, it's probably a good idea to have something like the cow/gold city just put hammers into fail gold.