You don't need to create another difficulty as lots of mapset are being ranked with map host made only 1 diff and the rest are GDs, but there are 2 things that you should consider:
1.
No one can make the ammount of GDs higher than you as a map host. For example, if you had 1 diff in your mapset, then all other people who attend to your map can only make 1 diff, no one are allowed to make 2 diffs or above. This is to not confused that GDers are the host of the mapset instead of you.
2.
Reasonable spreads are important. So far there are two rules:
- If the drain time of each difficulty is...
- ...lower than 3:30, the lowest difficulty of each included game mode cannot be harder than a Normal.
- ...between 3:30 and 4:15, the lowest difficulty of each included game mode cannot be harder than a Hard.
- ...between 4:15 and 5:00, the lowest difficulty of each included game mode cannot be harder than an Insane.
- All game modes within a beatmapset must form a spread starting from the lowest difficulty level dictated by the song's drain time. For difficulties above the lowest required difficulty level, the spread cannot skip any difficulty levels and there cannot be any drastically large difficulty gaps between any two difficulties.