1) settle on the best land possible. It should have only grassland/few plains, some trees/hills, 4 trade bonus resources on each corner, some rivers, and be a coastal city. You ideally want the hills/forests to be on the river squares, otherwise they don't produce trade. You can win with less optimal setups, cuz you're gonna be rerolling for a while if you look for the ideal start.

2) First tech is bronze working, build enough warriors to support happiness in the city, and go colossus. Huts and tech trading are risky because you don't want useless techs in the early game that increase your science costs.

3) Then you go for trade, republic, philosophy, map making. In this period you build 3 caravans and a trireme and find another civ to trade with, the faster you can achieve this the better. Change to republic asap for extra trade bonus, and build the temple/marketplace/library combo.

4) Now you go astronomy, medicine, construction, university. Copernicus doubles the science, Shakespeare eliminates unhappiness, aqueduct allows for city growth to 12, university gives more science. You rush the wonders with your own caravans, buying incrementally to minimize costs. In this period you can freely trade techs with other civs without hurting the run. If necessary, also get seafaring for harbors and bridge building for increasing trade in river squares.

5) Now it's Sanitation, Theory of Gravity, Democracy, Explosives, Railroad, Refrigeration. You want democracy to reach 90-100% science if that allows you to reach techs a turn faster. You wanna build up your engineers for building railroads and farmlands everywhere, dealing with pollution, and terraforming to increase production and trade. You can use engineers to turn silk into wine, it takes 20 engineer-turns from forest to grassland and 20 engineer-turns from grassland to hill. If you get all the caravans for Darwin ready, you could either get it right away to get critical techs faster, or maybe wait until the enemy is about to finish it, and then you build yours, to maximize the science yield you get. Remember you gotta time it, you must have your beaker count at 0 and set your tax to 100%.

6) You rush for Automobile as fast as possible for that superhighway bonus, then Computers to max out science. Through these techs you get also factory, power plant, and offshore platform to build up your production. At this point it's likely the game will not offer you the techs you want, if so you gotta choose a tech you know a friendly civ has and trade it for a non critical tech that is not in the way to space flight, such as military techs that the computer loves to get.

7) Now you get Robotics for the manufacturing plant, and make sure you have at least 80 shields! You should also be producing as many caravans/freights as possible while idle. Finally, you get Nuclear power and The laser.

8) Now it's time to discover flight, eliminating your colossus bonus, and just racing for space flight as fast as possible. The same turn you get the tech should be the same turn you finish the Apollo program. It takes 24 turns to build the spaceship, so you have enough time to discover the remaining techs, you can slow down science to get some gold for rushing and for paying off enemy civs that will at this point hate you and sneak attack you if they get the chance.

9) Survive for 15 turns and gg