I made some choices during my turns, I hope everyone agrees with them.
450 AD - check our status
I note that India has writing now, but still not MM. The Celts seem to be doing very well, but we cannot get to them before navigation.
We need to go to war as soon as possible. To finance our upgrades, I set research and luxes to 0 %, getting us 73 gpt, almost a Beserker per 2 turns when upgraded from an archer. Research on gunpowder is continued with a single scientist.
To get our economy going I make sure core cities have, or start building, aquaducts and marketplaces. We are overirrigating grassland and workers are clearing jungle while the core is not optimized. I will get some workers to mine the core.
460 AD
The Celts finish Leo's

Switch Bedeville to Sun Tzu, Crazybeard will waste shields to build an aquaduct next turn.
I trade spices+54 gold+7gpt for invention. I could have traded luxes but this way our rep will not be ruined when the traderoute is shot (I don't see the traderoute anyway).
470 - 500 AD
Upgrade some vet archers, Beserkers move to Ivory Woods, as do some the galleys. ACs are going to Iron City. Yes, this means I picked Carthage as our first target. I build horsemen in core cities from now on, they will upgrade to knights/cavalry. Non-essential cities with barracks build beserkers.
We complete Sun Tzu in Bedeville.
510 AD
Our scouting galleys reveal that Spain has to be on an island with no land connection to the Celts. This is good! Let's see if I can get Spain to fight the Celts for us, thus slowing the Celts a bit down. I establish an embassy with Spain, but she won't fight for everything we got. Trade mono for invention+13g+9pgt.
520 - 550 AD
Some core cities still need a market or an aqua, but our economy should get going pretty soon. Troops are in place or have marching orders. I suggest to go to war next turnset. We should be able to get research going again soon, making 93 gpt right now.
The save