I personally love India, early on you can make 4-5 cities big. I find with these big cities it is easy to make gold and science, and otehr stuff, so I usually win out on city-state quests and that makes it easy to have 3+ allied CSs after awhile. Then I expand via settlers or conquest to about 8-10 cities, then build up big and get the massive Ghandi war machine ready for steamrolling.
Keys at high difficult levels (emp+):
a) need at least 4 good spots for city growth, if you have a desert start you will lose,
so just restart
b) early DOW is doom. I find most civs (if you trade resources with them) will not make an early DOW, unless you are really close. If someone is really close,
just restart.
c) Once you can make comp archers, make enough to stop attacks. Sometimes you get attacked because of proximity or 'weak' army. With some swords and CAs, you can stop the attack and eventually they offer you gold and stuff for peace, which is a funny feature. On Diety, this attack can sometimes bring the end of your game, c'est la vie.
Once you get to mid-game, it is home free and fun. You just start consuming and razing weaker enemy targets, or you can go for culture or science or UN victories, because you will have this great base of big cities churning out everything. On Diety, you can still lose because sometimes on Diety some civ has consumed 2+ civs and is huge, but that scenario makes for an awesome end-game. A David verse Goliath, just incredibly fun as walls of units march at your borders, just have to hope you have enough late game resources inside your borders

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India is riskier than other more popular civilizations but it can win on any difficulty. I like it over other civs because it is less war oriented.