The Savoy Eight never actually existed as a standalone formation - they were a subset of the Chick Webb's Orchestra, and this group (Ella Fitzgerald and Her Savoy Eight) was meant to advertise Ella Fitzgerald as a band leader during her early days (the Decca period prior to Chick Webb death).
The first recorded evidence date back from 1936/11/19, and the last from 1939/04/21, for a total of 26 studio tracks all released by Decca.
While not essentially different from the Chick Webb's Orchestra records on which she featured in parallel (but the size of the band, obviously), the available cuts still have their historical importance as being the firsts on which Fitzgerald was actually given "leader" credits.
Content (and size) of the Savoy Eight varied over time, apparently depending on who in the Chick Webb's Orchestra was available, though the core of it was:
Taft Jordan, Sandy Williams, Pete Clark, Ted Mcrae, Tommy Fulford, Beverly Peer, Chick Webb - with additional performances by John Trueheart, Louis Jordan, Bobby Johnson and Hilton Jefferson.
If you're not looking specifically for Savoy Eight cuts, but rather "early days" Fitzgerald (or simply Fitzgerald), read Ella Fitzgerald notes for advices.
Otherwise, then you are either:
- a serious amateur: you may pick The Early Years Verve boxset, which is a very good set (if not exhaustive, with 16 cuts)
- a completist: unless you have the means to dig the original 78rpms, you need only The Chronological releases (the 1935 to 1939 volumes), which contain all the cuts - though - maniacs will notice that three of the tracks in the Early Years boxset are actually alternate takes instead of the masters, and that they are nowhere else available (If You Ever Should Leave, If You Only Knew, You Can't Be Mine), making the acquisition of the set mandatory for the real nuts.
Avoid everything else.