The schema are in the main snapshotter scripts. This is only some sample reporting procs. The snapshotter procs (Util_BuildSpaceLog) have the DDL and data gathering DML. Look in the Related content section under the Releated Tags section on the right sidebar.
One or the other, depending on whether you have sysadmin or just have dbo rights:
(The schema is the same for both for portability/upgradability but the DML won't populate the buffer cache columns in the dbo version because that data requires sysadmin)
The Automated DBA: Space Usage Snapshotter (sysadmin; central DB)
The Automated DBA: Space Usage Snapshotter Lite (non-sysadmin dbo)
Put a call to the snapshotter (Util_BuildSpaceLog) in a job. get some data for a few days, then run these reports and make up more reports of your own.
Oh if you use SSRS you can make SSRS do the running aggregates and differences/growth, making the T-SQL simpler and improving performance (T-SQL won't do well with running aggregates until SQL 2011; or whatever is after SQL 2008 R2), but of course the end user won't be able to copy-and-paste unless he were to export to excel (extra step, especially if RDPing for some reason to get the report)