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.
If cache size is larger than normal, it usually happens if there are a very large number of pages or if there is a dynamic part in JS or CSS – some themes/plugins creates dynamic javascripts and that is why the folder is filled up.
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