Uhhh well.
Generally on Deity if you just want to win you start either scout or builder, scout because early huts can get you gold or an early pantheon(harvest, forge), or hopefully hit a science or culture CS first. Builder to pop agoge early. Audible to slingers if you run into somebody early.
Try to boost archery, 3 to 4 archers and 1 to 2 warriors is enough to roll the first dude. Make sure you get writing and start spamming campus, harvest stone and chop wood with captured builders. Start rolling dudes. Keep all citys, get an early route to boost commerce to get some CH and routes going to city states for science, then culture. The gold helps.
Pre build a bunch of chariots and Uniwue horseman(alex uu upgrades to knights as well), make sure you grab iron somewhere(for knights). Once you have commerce, you can beeline stirups, then ussually university. Also get an encampment up in a core city, GGs help a ton, plus macedon UB has some bonus. Once you get stirups you can gold upgrade to knights. If you get knights around 60 to 70ish, you can start rolling dudes with just knights. Sometimes the gold doesnt work out or you hit it a little late, in that case i would bring some cats with you as well. You will be behind in tech most of the game but it doesnt matter because the A.I doesnt beeline like a human. If the game goes past needing knights, then you can line into cav, or line into artillery if you dont have niter for bombard.
No matter what it will be map dependant, but this is a basic outline.
Generally my goals are something rough like
First takedown before 40
Unis by 80
10 to 15 citys by 100
Try to hit as many citys with a colloseum as you can
Don't worry about amenitys to much, having citys sit at -1 is fine, and colloseum citys will be happy forever. Plus IIRC alex doesn't get war weariness or something like that.
Also dont bother getting most citys above a few pop. You just need most for the campus. A few early workers are fine for eureka and chops to push districts and units early, but there really not worth it until feudalism, and even then most of my tiles will remain unimproved.
I try to boost all the civics up to poly phi. Dont forget the military one at the top for rushed cav production to make chariots/UU horse faster.
Alexs UU swordsman is cool because it doesnt need iron and is a little stronger(but knights come so fast you dont need to spam them), his Unique horse gets GG points for kill IIRC, which helps.
His UA also gives you boosts when you capture citys depending on what districts are in them. But it doesnt change much, your still conquering pretty much everything anyway.
Important to note, alex doesnt really have any unique abilitys that affect how you play to much, mostly just buffs. His Uniwue horse going into knights is about it, as it means if you didnt start building chariots in time you can just build horses later, they will NOT upgrade to cav however.
I know this was rushed, but without map context this is just a general outline.
edit:Its hard to get guestimates exactly without actually having a map, but Pangea speeds things up a ton, no need for the caravel tech to cross oceans. I would guestimate on most pangea 12 player maps you can win between 150 to 200 pretty consistatnly. Sometimes somebody gets sticky, or walls up early, or lucky shots some of your units and that can add like 20 turns sometimes and is really annoying. But generally once you get really "rolling", the game becomes unlosable and its just a matter of time.
Also, forgot to mention, make sure to not rando die to religion spam, especially on pang. Aggressively DOW to kill missionary if you have to. Also forgot to mention, early game sell luxs for gold before everybody hates you forever, even if its your last one unless you really really need the amenity's. Use the money for upgrades.
also, if you have early culture making tiles I would work them so you can speed to early empire settler bonus, agoge, poly phi and the cavalry spamming card more quickly. Sorry that I don't remember the name of anything of the top of my head, but I figure if your playing Deity you probably know what im talking about.
Any questions just ask.