Definately Africa. It is the most underated region of the game. The key to understanding Africa is understanding that the allies don’y want to put too many troops in Africa either. Sure, from NW Africa they can then land onto Europe, but pushing troops too far into Africa, reults in the Germans dropping troops behing you. Very often Germany can take and hold most of Africa barring a major allied landing with minimal forces. Given said massive allied landing, the Germans not only caused a major flip in income between them and Britain for several rounds but also deterred a significant allied push.
My German opening always go as follows. Note we play with a few house rules that limit IPC production of all territories to IPC limit and Russia cannot attack with ships and planes on th efirst turn due to disrepair and parts shortages.
Purchase 1 TP, 7INF, hold 3 IPC.
Attack British fleet and Russian scrub fleet with bomber, 2-3 figs, 1 sub, 1 TP.
Attack British BB off Gibraltar with Sub and FIG.
Move TP with ARm to invade turkey (use three IPC). This blocks off the sub retreat.
German inf and ARm attack EGypt with blitz.
German FIg attacks British sub.
German inf pushed down west coast of Africa.
Eiether retake or fortify agaainst Russian first assault.
The extra TP guards the German fleet from air assault. It allows 1ARm, 2INF forrays into Africa whenever you want. It also allows 1Arm, 2INF forays into Russian territotries behind their main line.