Try to find or download the
Stages box set. 4 discs of Hendrix at his absolute best.
Woodstock is essential if you don't have it already.
The Berkeley Concerts
and the Box of Gypsys, which is basically all 4 shows that would later be compiled to make the Band of Gypsys LP.
There are literally thousands of bootlegs and shit out there, but these are the first to come to mind. Woodstock is always a given, but it probably was his best performance.