Luke and Matthew were referring to acquiring or buying a staff, Mark was referring to simply going as you are. The emphasis was that Jesus didn’t want them to excessively prepare for the journey, but simply go out with the sandals they were wearing and a walking stick they had on them.
One simple one was one apostle saying Jesus told them to go barefoot and with no staff and another saying he told them staff + sandals.
Luke and Matthew were referring to acquiring or buying a staff, Mark was referring to simply going as you are. The emphasis was that Jesus didn’t want them to excessively prepare for the journey, but simply go out with the sandals they were wearing and a walking stick they had on them.