I don't know what more I can do to further my skill in Civ V

You are grossly exaggerating. Most of the things you've listed are impossible to execute on a standard size Deity game (assuming Pangaea or Continent).

  • 90% chance of getting first Religion: I doubt it, even if you are playing Ethiopia or the Celts. Deity AIs heavily invest in Piety and Faith generation; there is no way you can do this unless you handcraft your opponents to be all Napoleon or Shaka.

  • 4-5 cities up by Turn 50: this is almost impossible to do in BNW unless you are extremely lucky with multiple AIs that like to befriend you. Even so, you will still need to hard-train 1-2 Settlers from your Capital, which will take about 20 turns and put you extremely behind. In addition, if you get 5 cities by Turn 50, all your neighbours will instantly DoW you for "building cities too aggressively".

  • Petra Rush: Good luck with that. Petra is extremely risky on Deity even if you go for Liberty and pop Great Engineer.

  • Rush shrine for first Pantheon: you can build Shrine first (which takes 10 turns), as the Mayans, and you still won't get first Pantheon 9 out of 10 games on Deity with 7 other AIs. This is because Deity AIs takes only 10 Culture to hit the first Social Policy - and since they get two Cities, they will hit Peity opener in only about 7-8 turns. After that they build Shrines 50% faster with two Cities and will beat you in Faith as a blank-slate Civ.

  • Alhambra - you will never get Alhambra on Deity. It's basically impossible to do as almost all AIs beeline to Chivalry and Alhambra will be gone in Turn 100. In order to get it, you need to not only beeline to Chivalry yourself (why would you even do this), but also somehow pop a Great Engineer to rush it. But why would you do that for Alhambra?! It's hardly worth the effort.

/r/civ Thread