Here is a furnace and crucible I built to melt aluminum.
Aluminum is pretty easy to melt and pour, just don't breathe the fumes, and wear some good personal protection including face protection, and boots perhaps.
I used the soft fire bricks from Budget Castings, but you can also use the hard bricks. The good thing about the soft bricks is that it is easy to cut holes in them with a hole saw or any other type of saw. for the burner, etc. Don't breathe the brick dust.
If I had to do over, I would just stand the bricks on end, and put them in a circle, perhaps cutting the sides to fit together, and using a little furnace cement.
I have even melted aluminum by just stacking fire bricks in a circle temporarily.
The crucible is welded together from heavy steel.
Some have mentioned that a steel crucible will contaminate the aluminum, but I have not seen any signs of that, and a heavy-wall steel crucible is very tough and long-lasting.
The pouring shank needs to positively lock into the crucible so that you can tilt the crucible beyond horizontal without any danger of the crucible falling out of the pouring shank.
I will look for a pouring shank photo (the one I use).
I use propane to melt aluminum.