"Ninja" and "samurai" are their own plural just like "anime" so saying "ninjas and samurais" is not necessary. It's like the word "moose".
Ninja mostly consist of ronin and farmers. That's basically it. There were very few high class ninja. Their day job was farming and their night job was covert espionage.
The ninja that you see in anime are extremely exagerrated. Example: Naruto. The closest thing to a "real" ninja there would probably be Shikamaru. Working in the shadows. Ninja aren't loud, obnoxious, and they don't wear orange jumpsuits.