What is your main router?? Make and model please.
Who is your ISP and what type of broadband do you have?
If you are using Apple router.. the newest ones are useless because Apple removed SNMP.
Earlier ones you can use a simple piece of software on your mac could peakhour. Just search for it. But there is no controls.. it is simply going to tell you which devices are pulling all your bandwidth.
Basically you need a router with true controls.. in the past I would recommend a 3rd party firmware called gargoyle.
See this post for more details.
Re: How do I enable SNMP on Airport Extreme 802.11ac?
The problem now is to find a suitable router.. not at all easy.. I am about to test a current model linksys.. if that works it would be great.. otherwise I recommend you go for an Asus router RT-AC68U or above.. these do not have quota controls like gargoyle.. but it has excellent QoS and will track usage.
Apple provided nothing of this nature.. and in fact removed the only monitoring that was possible in latest models.. which is part of their program of making stuff domestic as possible.