Leather profession + level 2 leather building + leather follower so that you get 22 resources per day
Skinning or buy leather.
Barn for savage bloods
Trading post for resources which are needed later
War mill for follower tokens + extra rolls (trading post offsets this cost)
Barracks for 25 follower limit + easier time farming mats with body guard like viviane
Salvage yard for more tokens and gold
Storehouse to store all of your tokens for later use
Followers are a whole separate topic but the must haves are:
Blook
Harrison Jones - Power leveler
Arakkoa follower (either spires completion or buy it for 5k gold/apexis)
Pleasure bot
Goldmane
Now you have the 4 followers that you can get the training books via missions for and you can make the 3 follower super team. There are other threads that talk more about that.