No free software is gonna be anything you want, so Id stay away from any of those. Someone already mentioned Ableton Live and yes that is a very good program for mixing/sampling etc. I would also look into Logic if you have a mac. Logic, imo, is the best program out there and it has so many features and options that Im sure you'll like it if you choose to go that route.
I would steer clear of Pro Tools, everyones gonna come into this thread and tell you Pro Tools is industry standard and thats what everyone uses. They are right, but that doesnt mean its the best program...
Summary - Ableton or Logic are your best bet.
/inb4 Pro Tool n00bs