Reports

Hello, Im new to fortigate and trying to get the gist of it all. Especially the reports needed by my organization and the default ones are not what we are looking for. Tried to custom make a report to suit our tastes but the data it shows isnt exactly whayt i hoped it would be. Currently running Fortigate 60E v5.6.5. Mainlt want the top 5 users who have the most internet usage along with the sites they frequently visit, sessions etc. If anhone can provide assistance please.    Thanks :)