Iron Working is almost never a correct tech to self-research during the initial expansion phase.
Jungles take far too many worker-turns to clear; building extra workers to keep up with jungle-clearing instead of more settlers to just get more cities that have more tiles that don't need jungles cleared is not a good trade-off. Treat those tiles as dead spaces until your initial expansion has slowed. If you want to expand militarily, swordsmen are a bad gamble; you either go quick with axes or chariots, or the slower "rushing" unit is horse archers. If you're not going for any of those (and don't have a relevant unique unit), you wait for Construction. Revealing Iron isn't all that useful if you already see a source of copper, horses, or ivory. And the trading value of Iron Working research is minimal, because the AIs love to research it themselves - so you often can't trade it to them by the time Alphabet trades open up, but can get it from them relatively easily unless you're seriously out-teching the AIs.