To ruin something means to severely harm, damage, or spoil it.

To ruin someone means to cause them to no longer have any money.

Ruin is the state of no longer having any money.

Ruin is the state of being severely damaged or spoiled, or the process of reaching this state.

The ruins of something are the parts of it that remain after it has been severely damaged or weakened.

The ruins of a building are the parts of it that remain after the rest has fallen down or been destroyed.

If something is in ruins, it is completely spoiled.

If a building or place is in ruins, most of it has been destroyed and only parts of it remain.