I use a random leader, usually. Any leader is capable of sweeping. Sure, play to their traits' strengths and starting techs are helpful, and of course you'd like to abuse the UUs and UBs, but any leader can perform these sweeps.
I don't like playing Vanilla over BtS, but since you seem to think it's much harder I gave it a try. Made it up to 720 AD where I'm in a pretty nice spot, should have a straight-forward win available. I don't know why someone would willingly choose to play on a Standard size map with extra civs, that plays to their early expansion advantage. You're meant to scale the map along with civ # for a reason. Playing as Catherine is very nice for this type of game though, the Creative trait is great.
I took cities at the dates below:
#2 : 2640 BC
#3 : 2360 BC
#4 : 1560 BC
#5 : 825 BC
#6 : 400 BC
My tech path: Agrculture - Bronze Working - Animal Husbandry - Wheel - Pottery - Fishing - Writing - Mathematics - Masonry - Sailing - Code of Laws - Civil Service - Mysticism - Meditation (Now tech trading begins, was on my way to tech Monarchy)
After that I stopped noting my path, as it's mainly a dart for techs the AI ignores (for trade bait) and darting for Liberalism.
Started pretty standard, did 1 worker steal and expanded towards opponents quickly so they couldn't steal the land from me.
650 BC 1st GS is born -> Academy
425 BC Notice Montezuma is plotting war, likely for me. Stop wealth building and start prepping Axes and Spears.
225 BC Montezuma DoW me
1 AD: Napoleon techs Alphabet!
- I get 120
and Priesthood + Iron Working + Archery
25 AD: Mansa techs Alphabet!
- I get Alphabet + Metal Casting
- Trading with others gets me: HBR + 80
; Monarchy + 320
; Calendar + Monotheism
100 AD: Capture Montezuma's Flood Plains city
250 AD: Peace with Montezuma, gain Construction + 80
580 AD: Notice Bismarck plotting war, likely for me.
700 AD: Bismarck DoW me
720 AD: His stack (of 5 units?!) crashed into my longbows + wall in city, easily beat his 1st wave, the Vanilla AI seems incredibly stupid compared to BtS AI.
Vanilla AI may have stronger bonuses so they can tech faster, but when it comes to war they trickle their army in small waves and retreat their units as if dancing around like a 4 year old. It's pathetic, this actually seems easier than BtS even though it's on Immortal and they're supposed to have higher bonuses.
From here I'm ahead of most in tech and should win Liberalism (though I haven't met all AI, one may be closer. Egypt and I traded Education + Philosophy a turn ago, so maybe they'll get it if they tech for it.) Either way, when I go for Cuirassiers or Cossacks, I know for certain at least 3 of the 5 other civs on my continent won't have Rifling to help defend. I'll watch carefully and choose my 1st target based on how technologically backward they are or how close they are to a good military tech (meaning I may want to hit before Mansa gets Rifling, maybe I can wait and make him the 3rd target, or maybe he needs to be the 1st, etc.) There's no doubt that I can take at least half of my continent, maybe the whole thing. There are 4 continents in the game, 2 like mine, containing 3+ civs, 1 has Persia all to itself. I'm scouting the seas for other, uninhabited islands, but all 14 civs have been discovered by maps, just not met yet.
The only difficult part of this game was claiming the land at the start, but the Creative trait is very helpful and I was sure to rush, chop, and whip my settlers for my 2nd and 3rd cities. I could've gotten faster 4th, 5th, and 6th cities, but didn't want the higher maintenance costs so early. I left a Settler at the 4th city spot in case Bismarck tried to expand in that location. I never really felt any pressure beyond the settling phase, I wouldn't rush for any wonders because of how many civs are in this game - makes it very hard to finish a desirable wonder. I was worried when I saw Montezuma (notorious warmonger) is right next to me, but after seeing how Vanilla AI fights, I can't help but laugh. I didn't even plan on attacking a city of his, but after realizing how few units he actually had and how he would crash jaguars (swordsmen) into my axes and leave small stacks of 2-3 all around my units for easy clean ups, it became easy to push for his nearest city.
Also cathedrals suck. They're only good for culture wins. If you're content with staying on 6 cities and staying peaceful, sure, play that style on some games, but in all other games cathedrals are expensive buildings that give a bit of +
and may expand your borders a bit.
As for your game with Ghandi killing you, that's unfortunate. Check the civ screens for when they are plotting war (We have enough on our hands right now) so you can prepare properly. Also that's very few units to have at that point, did you lose other warriors to barbs? If it's a standard map with 17 civs, there should be very little room for barbs to even spawn. And teching archery yourself may be a mistake, especially if you have horses or copper nearby.