By his virtue, Lan Wangji doesn't loot. On the final day before they board the train and the mission is complete, Lan Wangji may find a way to pay for the food in the market hall with the world's currency. Probably pay for the clothes too. He's stocking up food/drinks as he's going to need a lot of food to prepare to cook for an upcoming birthday/new year gathering that he wanted to hold on the train.

Speaking for his family:

Sizhui's loot: neat rocks, rabbits, vegetables and flowers if he can find them.

Wei Wuxian's loot: Booze, liquour, spirits, etc.

/being an enabler