I think you'll be happier in learning if you don't start out worrying whether you 'should' have started with something different.

The first 6string banjo I saw was promoted as a cross between banjo and guitar. Sounds like a banjo and plays like a guitar..so guitar players could pretend to be banjo players without having to learn new stuff.

ANY instrument is a step in the right direction.

Whichever kind you get next will be easier to learn--simply because a lot of the basic foundational stuff you pick up with your first instrument will carry over.