If you already have a drag strap (which I assume you do), then a MG man would be the easiest to build. The gear would just consist of a P08 holster and belt (with buckle). You could throw in a bayonet or a trench knife if you wanted to. Not every MG man qualified for the MGSsA insignia, so you could even leave that out. A Bluse with infantry shoulder straps, trousers, boots, a Halsbinde and helmet would round things out.
Depending on what you envision, I would forget the storm-trooper.
Extra items for an infantry set would be, Tornister with Mantel- and Kochgeschirrriemen, Messkit, Zeltbahn, Zeltbahnzubehörbeutel (with rope, tent poles and pegs), overcoat, cartridge pouches, breadbag, entrenching shovel with Spatentasche, bayonet and frog, bayonet knot, Gew.98 with sling & a canteen. Quite a list with a total cost (if you could find everything) of about $5,000.00.