The end goal is to replace the center tile by building up resources through successive rolls and tile placements.
Barrens tiles gets you stone which can buy more Gaia's Gift dice
The Gaias Gift dice will also let you turn Barrens to Grassland which produces wood.
Wood can be converted to The Wilds dice which has extra mana and is also used to make Final Battle dice
With a few Final Battle dice you can get the mana needed to construct the conquest over the center tile. Defeating the black square and earning victory.
I'm fully aware it's not intuitive in anyway haha. Looking forward to expanding on it post jam