What is the best way to organize workflow in the cloud?

Question

System administration

A small company is in the retail business. Many documents, contracts, etc. are connected with this.
We decided to try to transfer common documents to the cloud. Please suggest some cheap service. Computers ~5 pcs. I would like to have a custom sharing system, access accounting (who changed what and when) and backups.
While the eye fell on dropbox. Are there any other alternatives?

Answer 1

OwnCloud https://owncloud.org/
seafile seafile.com/en/home

Answer 2

In general, while the choice fell on Google Drive. 15 GB starting + and so sometimes we use Google dox.
Sharing is, file revisions too.