You played it well in Decline 2, any advice? I tremble at the thought of establishing a full blood economy and balancing it with research and all (also, all the virgins).
I played it OK, and EA is a bit different from LA, mostly on research priorities. Early game you play like everything else, grab land etc. There's a lot of info around for best practices on blood hunting, but roughly choose 5k population provinces, and use your cheap priests with sanguine rods. They are also your best researchers. Make a million priests basically.
So you want Const4 pretty quick, but since LA Mictlan is not as much of an early powerhouse as EA(because everyone's tech has surpassed you) you might want to focus Alteration first in case you run into trouble, where you can fairly easily start casting protection, body ethereal, quickness, etc. on your jaguars and other troops. You won't have a huge need for or economic base set up for blood hunting early anyways.
That said, some people go straight for blood 4. You can get enough slaves even without rods, and going to B4 opens up some great tools early game. Ozelotls, Lesser Horrors, Hellfire, Agony, etc.
Also hotkeys, Z and V are your friend for transferring/pooling slaves. Use scouts to ferry slaves. Mid game you've got some great national blood summons(Civateteo and Tlahuelpuchi fill a couple nice roles, Ozelotls and Beast Bats can give swarm potential), as well as the rest.
Try and find some crossbows ASAP. You'll be a target for anyone who has archers or heavy armor, depending on your bless.
Rain Warriors + Rain Priest can get you underwater just fine, with maybe 10 warriors.
Dominion pushing with things like Vengeful Waters is an option and even Dominion killing somebody who is noticeably weak. That's kind of hard though, and takes patience.
Use Tribal Kings to round up slaves as arrow catchers and chaff.
I don't know, I'm sure there are other ways to go about it, but that's the basics as far as I know.