After one day of surfing my CCleaner is delete close to 1GB of data, that include cache, tracking cookies, browsing history...
But the majority of these 1GB of data surely wasn't browser ?
The default setting for firefox is to keep max. 50 MB of data in the cache. Other browser have a similar limit.
I am not sure whether browsing history and cookies count towards this, but this shouldn't be more than 1MB anyway.
You might want to check what CCleaner is deleting (besides cached browser data) from your computer