Add each building you own, set current → target level, and the ledger totals exactly what to trade for. Windmill caps at 2; Silo, Composter, Beehive and Sheep Pen cap at 1; everything else is unlimited.
Every plot is 9×9 (81 tiles). You start with 6 free plots (486 tiles). This totals footprint area only — it won't tell you exactly how shapes fit your irregular plots, just how many more 9×9 expansions you need.
Workers are a hard limit: every production building drains workers to run (at its current level, not target), Houses are the only supply. Happiness is different — it's not pass/fail, just keep it between 40 and 100: below 40, construction (Pigsty, crops, etc.) costs more cash; above 100 does nothing extra. Houses cost happiness; Farmhouse, Fence, and decorations supply it.