Datastores can only store player data, how would I store,for example, the amount of money a store through ALL the servers has made, by selling items? (aka global counters)
You can't store Instances. Roblox doesn't serialize them, because JSON has no support for them, and Roblox doesn't support binary data structures for storage (Truth - Roblox actually doesn't like a lot of binary values).
The solution?
Store the information which describes the Instance. Is it an IntValue? Store the number. Part? Store the information to make it, such as the name of the thing you cloned it from. Weapon? Store the name. Serialization is an important part of storage which was missed out from DataStores for some unknown reason.
DataStores can only save tables strings or numbers, no objects or classes can be stored.