For two crabs you’ll need 20 gallons of aquarium space. Mostly everything on Amazon is a bundle for fish, so it comes with stuff like the filter, heater, etc which those you don’t need. I know petco and petsmart both have just regular glass tanks with nothing else, and both of them sell glass lids as well to fit the tanks!

As for toys: a bunch of people’s (mine included) crabs like the coconut huts, cholla wood, and also things like hammocks and vines for them to climb on.