I've created several unique playlists to cater to my own interests. For example, Short Punk made up of Punk songs under 1:30, Soundtracks, 5 Star songs not recently played, Longer songs, etc. To fill the gap I created a playlist which included songs which were not on any other play list, with the exception of my "star" lists.
Match all -> Playlist -> is not -> Favs
Playlists -> is not -> Recently Played
Playlists -> is not -> Long music
Playlists -> is not -> Short Punk
etc. etc. Cater to any limit you like and I chose only checked songs and live updating.
My list has about 1000 songs from a 2600 song library.