But, I'd love some advice on better builds/upgrades etc. I really blew big parts of this game, so any advice you'd like to give, I'd be very happy to receive.
What I've learned and been told is that the AIs respect offensive units more than defensive units. So having 6 MDI is as effective as having (I'm guessing here, but the ratio should be close) 9 pikes or muskets in preventing over aggressive AIs from demanding and declaring.
Its quite funny to me how this game has gone. I came in very confident that my Emperor level play was completely up to snuff...
I know what you mean. I've lost a couple of Emperor level games I should have won due to my poor timing or development, and the flood plains start here was difficult. You have great pop growth, low production, and just when you think you have it figured out, disease drops your pop by 2, completely messing up your settler production plans.
Generally you want to build a couple of exploring warriors early, then pump out settlers and workers. If you build any military units early at all, then you need to stand them out in the fog to prevent massive barbarian uprisings from eating your settlers, workers, or gold, or station them near enemy lines if you are planning to attack.
Every once in a while, check to make sure you are not military heavy, and do not be shy in disbanding extra units in towns to cut back on their upkeep (and help finish builds).
Don't be afraid to give in to demands (or anticipate demands and trade to avoid or maybe just prepare for some war happiness). Frequently if the AI demands, they have an offensive unit next to a town or vulnerable unit.
For this game, I focused on a peaceful cohabitation and only had units stationed in the border towns between me and France. The results are in the final thread. Peaceful games are not always successful, and they generally don't generate high scores, either. In this game, my objective was to gain the tech lead and then keep everyone else drained of gpt through trades, which allowed me to rush way ahead in the tech race, shooting for a UN or spaceship victory.