As a noun necessaries
is necessary or indispensable items.
As an adjective necessariest is
Necessary or indispensable items.
* 1908 ,
- Mechanically he returned home, gathered together a few small necessaries and special treasures he was fond of, and put them in a satchel; acting with slow deliberation, moving about the room like a sleep-walker; listening ever with parted lips.
* Most necessary is significantly more common.