Do the Main OPS first then Extra OPS later. When you get access to Mother Base. The game does offer a tutorial on how to assign jobs to personnel under Staff. There is also a tutorial on how to use the R&D section to develop weapons and other technology that will help you in the game. Go to Mission Selection. After selecting a mission, in Mission Details. Go the bottom and select Briefing Files. They are audio recordings of Miller talking to Snake about the missions and things related to Mother Base.
The more you play, the better soldiers you can recruit. Better weapons to build. Soldiers specialize in certain skills and should be assigned to teams that suit their talents. Engineers to R&D team. Cooks to the Mess Hall. Doctors to the Medical team. Spies to the Intel team. Soldiers to the Combat team. Press the Help button for more information about the menus. It seems complicated at first but just keep completing missions and you are able to build Mother Base into a badass army.