Quintus,
Everything you need for Global 39 exists on HBG’s website. If you have a recent A and A game you have many of the necessary pieces already.
I suggest:
Germany and Axis Minors sets in black, grey, yellow, dark grey, and mustard. Marines, a US supplement sets (try at least two), Japanese supplement, Russian early and late war, neutral sets in at least five colours, 20 each of naval base and air field markers, and at least 20 twelve sided dice in the colours you prefer (I went with red and white at first).
Get SS, Guards, Commando, Airbourne, Fallschirm, Marines, SNLF etc markers.
My understanding is that the just announced expansions are to add a new dimension to the game and bring forward battles on an operational level within the larger strategic context (I am super excited about this).