Hard to say what was "supposed" to be their complement as they at first shared aircraft with JG 11. In theory, any JG Gruppe was to be made up of 3 Staffeln and a Stab but reality replaced theory in numerous cases especially later in the war.
JG302 was established in November 1943 with the II Gruppe being formed by renaming II/JG301. III Gruppe was formed by renaming III/JG300.
At the end of December II/JG302 reported only 2 dedicated aircraft on strength and III/JG302 none. This was due to the sharing of aircraft with JG11.
Source: Reschke "Jagdgeschwader 301/302 Wilde Sau"