Looking over the save, I see the concern about our unit support costs, currently we're paying 64gpt. But I don't really see any expendable units, except for a few reg warriors on East Island, which I'd like to replace with spears, at least. We are still considered weak compared to everyone but the Byz, so we can't afford to disband units, and we certainly need our workers. The only other option is growth, so I am going to focus on getting more towns into cities for better unit support, and maybe build another one or two.
The tech situation isn't any more hopeful. Everyone else has at least Invention, and based on the numerous Musket sightings, Gunpowder must be pretty common as well. Our only chance for a 2-fer is on Monotheism, which China and Korea lack. Of course, with our tarnished reputation, buying Monotheism won't be easy, in fact I can't get past doubtful right now. Our best bet would be for Korea to get it before China, as they will still take our credit. I do notice Carthage has Spices for sale, at 11gpt. We can drop lux to 20%, saving 16gpt, so it's a net gain of 5gpt, I make the deal. We might even be able to drop it further once the markets finish.
About the only good news is the Wonder cascade is dead, but the bad news is that's because the AI built them all already.

Lisbon in particular is loaded with 4, including the Great Library, that would be a nice grab about now. (But not very realistic...) In fact, Lisbon is already in the running for a 20K city, if it gets that far, they are at 1472 culture. That happens to be almost triple our whole civilization. Looking around, most of our border cities have no culture at all, that's just asking for flips, which we can ill afford. I think I've discovered another priority for this reign.
Other than the Spice deal, and some MM to speed up a couple builds, there's not much to do, so I hit enter.
IBT: Istanbul-Spear>Temple, Bursa-spear>duct, Uskadar-Library>settler, Sinkope riots and gets a taxman.
260 (1): Not much, move some workers to mine grass, clear jungle. At the Iron city, the current worker will complete the road next turn anyway, so the other two move to chop a forest and hurry the harbor along.
270 (2): Iron road is complete, that worker moves to chop another forest. No point in rushing the harbor yet, let our mainland harbor complete, and the forest chops to reduce the cost.
IBT: Edrine-market>library, Konya-harbor>duct.
280 (3): Not much, send a galley back toward Byz waters to start exploring again, shift a spear to East island.
290 (4): OK, the opportunity we've been waiting for! Korea has Monotheism, and China doesn't. Korea takes our Ottoman Express card for 30gpt, and we get Monotheism, but China says that and our 280g cash isn't even close to Invention.

So much for our 2-fer chance. We don't really have much more gpt to offer, anyway, even if they did take our credit, so this may have been a bad deal, but at least we can see a little further into the AI's lead. Portugal and Byz are up Chivalry and Theology, Carthage has just Chivalry. We are just too far down to broker our way out of this one, I think.
IBT: Istanbul-temple>library.
300 (5): China has Monotheism now anyway. Lisbon is at 1617 culture, gaining 29cpt.
IBT: Iznik-market>duct. Byz and Port start Sistine's.
310 (6): Forest chops are done, so I pay 72g to rush the harbor at Salonika.
IBT: Salonika-harbor>library (I'd hate to have our iron flip away!).
320 (7): Nothing much, more worker moves.
IBT: Istanbul-library>pike, Aydin-Market>library.
330 (8): Nothing.
340 (9): Nothing else, except Theo asks our galley to leave. Finally brought our budget back in balance.
IBT: Istanbul-pike>pike, Edrine-library>MDI, Antalya-market>library.
350 (10): Did the worker moves, the Sultana is docked off of Uskadar, most garrisons unmoved.
Those last 3 builds are obviously open for change, as nothing has accumulated yet. Also, Bursa will finish the duct this turn, and should be MM for population growth for a while, but will be available for military production.
At this point, we probably need to discuss our next direction. I don't see any brokering opportunities in our future, so if we're going to climb out of this tech hole, we'll have to use the pointy stick. Unfortunately, we're still weak compared to our neighbors, but now that we have Iron, we could start building some kind of offensive force, mostly MDI's and some trebs. Without being able to upgrade, it's going to be a more gradual buildup, but Istanbul is at 15spt, and can build enough pikes to beef our defenses, which will free our obsolete warriors and archers to be fodder at the front.
China is probably the easier target, although they have less tech to get, they also don't have muskets yet, and would give us some much-needed expansion room. Even if we could get just 3-4 cities, and Invention, we could get back in this game, I think. They do have Chivalry, but no horses, so we would be on an even basis, unit-wise. Anyway, it's something that will take a couple rounds of concerted effort, but I think it's our best chance to break out of this stagnation.
A couple final notes, the harbor at Kafa will finish in 2 turns, connecting the Eastern island to our luxuries, and then our tax/clown/scientist can be put back to work. I put the scientist on Theology, figuring our priority now would be to somehow get Invention, so we can take our time on the upper branch. Also Uskadar is working on a settler, due in 5. I had intended to use him to settle on a border jungle spot NW of Istanbul. This would poach a few tiles from Carthage, including a mined hill on the river, and share a first-ring tile with a city, but would also be first-ring to our capital, and with a quick library might only be a minimal flip risk. It would definitely be a productive location. Otherwise, there's not too many spots left, or it could be saved to resettle any cities that get razed in any upcoming wars...
Here's our Republic, with the proposed city site marked in red: