So, this will take you some time. Don't get ahead of yourself, this will likely come during/after the last story arc with Sigurd. You must complete each raid location and each Alliance that grants you supplies as well as the ones that increase your population. You will, after completing all raids and alliances, conveniently have just enough raw materials to build everything, so the only issue is supplies. The final addition to the cattle, grain, and fowl farms cost 1200 supplies and 90 raw materials. (another edit: you must do this upgrade 2-3 times. for me the first UPGRADE cost the same as building the farms, the next 2 UPGRADES required 1200 n 90. (maybe the game glitched out idfk, i also did it REALLY early in the games life so it coulda been reworked.) Loot every supply box you come across, I had to spend two hours trying to find 1000 supplies last night so to avoid that I'd say just thoroughly loot every monastery, and big cities like London and wincester will also have plenty of supplies, as well as the smaller villages and river raid locations (not the main raids, the smaller ones that arent marked with red-axes on your map) (credit to JewsusHKrist for pointing out the village and river raid areas being good areas for supplies.) supply boxes are more...homemade? looking, as opposed to the weapon and armor upgrade materials chests which look like actual stereotypical video-game chests
Edit: Jan. 16th. 2021. There are 3 upgrades to the 3 farms after you build them. If the buildings have signs next to them, they must still be upgraded further. When looking at the village through your Ravens point of view, any buildings that require upgrades will have their symbols outlined in blue.
I hope this helps! Good luck achievement hunting :)
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