The average size of a cached page should be about 200-400Kb. That means if you have 1.000 pages the normal cache size will be about 200-400 Mb.
Clear all cache, then do the following steps:
1.) Enable Separate Styles and Separate Scripts in Optimization settings:
2.) Exclude unnecessary post types: autoconfig should find most and exclude them automatically but you can add them manually: Settings > Caching > Exceptions> Exclude Post Types