Best way to workout at home?

Okay, i'm 23 years old and have no muscle definition at all. I'm wanting to build some up but the gym is not an option at the moment. I'm mostly interested in a full upper body workout and wondered what I should be using to achieve this or even just a partial workout that includes the biceps, triceps, pectorals, shoulders, stomach etc. Can I get away with a set of dumbells/barbells, a plain bench and the floor or should I be looking to buy extra equipment? A home multigym is out of the question as I live in an upper floor apartment. Thanks