The recommended size for 1 site collection is maximum 100 GB. If you think your application is going to be larger than that, I will suggest you go for another site collection.
A site collection can be as large as the content database size limit for the applicable usage scenario.
In general, we strongly recommend limiting the size of site collections to 100 GB for the following reasons: Certain site collection actions, such as site collection backup/restore or the Windows PowerShell cmdlet Move-SPSite, cause large Microsoft SQL Server operations which can affect performance or fail if other site collections are active in the same database. For more information, see Move-SPSite.
SharePoint site collection backup and restore is only supported for a maximum site collection size of 100 GB. For larger site collections, the entire content database must be backed up. If multiple site collections larger than 100 GB are contained in a single content database, backup and restore operations can take a long time and are at risk of failure.
SharePoint Server 2010 capacity management: Software boundaries and limits
