A folder of good frames is not a portfolio. Coherence — of subject, light or point of view — is what turns pictures into a body of work.
The strongest portfolios repeat a question rather than a subject. A photographer might shoot markets, doorways and hands, yet every frame asks the same thing about how people occupy a place.
Ten photographs that belong together beat forty that merely coexist. The edit is the art form; shooting is only the raw material.
More on the shooting itself in craft.