To be frank, you don't need to change much at all, IMO; you are bringing in 500+gpt, so getting Espionage at this stage of the game is not essential. I'm a little in the dark as to how far along the tech tree many of the tribes are - you are at war with most of them, and they won't acknowledge your envoy (and I don't have CAII installed yet) but of those that I can talk to you have three good potential trading partners (Korea, Ottomans, Celts), and crucially you have maintained a clean rep. I'm assuming some of those with whom you are at war are two or three techs behind, and therefore would make it possible to recoup much of what you outlay; I suspect you don't need too many lessons on trading since you have got this far, though.
I think it was perhaps an error of judgement to have DOWed the Ottos; I'm guessing it is they who have brought in so many enemies against you, since they have techs and gold to offer; also, I don't see them as your greatest threat. IMO, Korea are the ones to watch - I see they have amassed over 30,000g.
My advice would be to end as many wars as possible; Ottos will make peace, and once they do many of those who they allied against you will be willing to talk pretty soon. Don't let pride get in the way - if they want a small bribe, give it to them. The exception to this is if they are a lame duck giving you war happiness.
On a map this size, I feel your best bet for getting the resources that you will need to launch will be to trade for them, and you need peaceful relations for that.
I see the UN is not enabled, so that obstacle is removed.
To put it in a nutshell: keep it peaceful, and keep trading the way you have been. You will need to keep your nerve once the SS parts are being built, and be sure to have a good pre-build going for that last tech, which I suggest you buy since a failed spy mission will leave you chewing your nails for another four turns until you can try again.
Edit: BTW, Babs have 840g going begging - better in your pocket than your rivals.
Edit again: OK, I've got CAII running and you have a number of alliances against the Ottomans; that's unfortunate, because it's highly desirable to maintain a clean rep in a zero-science game.
My advice is slightly amended to: make peace when you can do so without ruining your rep, and resist the temptation to make any more alliances.