The rage at the moment is 1 x 12 speed. Personally, I don't think that this is for everyone as it limits your range. As a beginner, I don't think the number of gears is make or break.
On a mtb, hydraulic brakes make a huge difference. V brakes (rim brakes) are also pretty fine, but mechanical discs are rubbish. If you buy a bike with mechanical discs, your first upgrade would be hydraulic.