Unless steep or with lots of tree roots or embedded rocks, those sound like easy conditions for a mountain bike, and almost anything would do. Full suspension would be excess weight for no benefit. On many trails like that you don't even need suspension, just grippy tyres.
Disc brakes are nice, especially in the wet, but not essential in those conditions unless you're going very fast. However assuming you're buying new, decent quality (and plenty of rubbish ones) mountain bikes are likely to have discs.
Gears depend on the hills you expect to encounter, as well as the surface, but at a beginner level you don't need the latest 1x11 setup.
Wheel size, so long as you don't find something out of the ordinary (which makes tyres hard to buy), isn't such a big deal either as a beginner. You probably want either 29" or 27.5", but I'm taller than you and haven't had trouble on 26" wheels.
Overall you want something maintainable where you are, so if hydraulic disc brakes are rare, make sure you've got access to spares and repair services before spedning lots of money on them; if 26" wheels are rare, buy something else, but in many places 26" is a common size.