Oh, dear.
The way I play the Extended Original game is to
start on Alpha Centauri. Just think -- a whole planet all to yourself, with no enemies except the occasional barbarian. The only units you need to produce are those sufficient to explore, find goodie huts, and your settlers. You don't even need to defend your cities, because there's nobody there to attack you.
Now you may wonder -- how do I get the tech that other civs get?
Just build the Great Library first -- as fast as possible. You'll get lots of tech that way. And invest heavily in libraries and marketplaces. Build the Wonders that give you knowledge, money, and sufficient happiness to stave off the civil disorder problems.
I just try to build the wonders myself -- after all, I won't be able to get at them if the Earthpeople build them first. I'd have to build my ship, go there, and then try to get the wonders (if they were still around).
Build the diplomacy-granting Wonders just so the Earth civs can't use them. Ditto with the Great Wall. You won't really need them, but you'll also deny them to the enemies.
So you can spend most of the game exploring, building, and increasing tech. Then, when you're getting into the modern tech, you can start to build your military units to defend your cities, and get some units ready to go for when you reach Earth.
By that time you should have a good sum of money on hand. I suggest rush-building your spaceship as much as you can. Ditto earlier for your libraries and factories. You want knowledge and production, fast!
Then you won't be stuck at half a spaceship and 20 years to go!
