Network Bandwidth Usage
Usually, how much bandwidth does your network eats or requires for a maximum of a 120 users?
10% of it uses skype to call clients. The rest uses it for browsing, email, and chats.
Any suggestions on shaping up the network bandwidth aside from Qos?
There is no definite answer to that - to say the least. It is something that will be very dynamic from hour to hour to month to month.
I cannot answer your question without knowing the business sector you are in.
As a general rule I would give SKYPE and e-mail priority IF they are being used for customer contact.
The rest goes to the bottom of the food chain.