Create item on client or server.
Send skill to server.
Server send skill to clients.
Drop item on server and clients.

Now, if you want to check if the client actually has this item to drop, you could always have "iventory boxs". So, every machine knows what is in each space of inventory. This way you dont tell the server and clients "drop item x". Instead, you say "drop inventory box x". It will work if you label each peice of inventory in it's own container... and it's in the same container on each pc(you place it in the container upon creation, the container really just contains a pointer to its item/items). This is quick thinking though, so mabye it won't work(I never worked with an rpg inventory before).