The type that was easy to read and predictable, but it has its own quirk.
Those kind of character were easy to make because they're just 2D characters with flat personality, but they have predetermined reaction toward certain stuff.
They're just some people MC talks about insignificant slice-of-life topics to sometimes serious Canon topic, depending on the NPC status. They can simply in the idle times when both coincidentally met. A.k.a in classroom, in hallway, in market, in mall, in the bus, in the neighborhood, etc. And then both may not met again for another chapters, arcs, volumes, or even books.
It helps so much to increase the presence of character with small role, easy to replicate by changing little details, and the best of all : No need to worry about keeping tracks of their complex mental issue and personality depth, as they're just predetermined NPC with clear pattern.
Just make sure to make they still interact with MC on the future arc of Story Canon timeline. Keeping notes about their future presence isn't as hard as keeping track of Main Cast's psychology status for the whole volume. Probably something like "Joe became owner of materials store and met MC on the hotel in Volume xx", and ignore it until the volume started.
The thing we don't like is when we add too much of them, or when we forget their scheduled appearance on the current volume. Or even worse, we already past one or even two volume from the supposed appearance of them. It's not like they're that important, but small missed details that have been prepared so long would be wasted opportunity.