9. Don't Auto-Assign Your Staff
There's a huge temptation when it comes to the myriad of screens governing your ordnance in MGS, to just hit the 'Auto-Assign' button for your recruited soldiers, as it can be quite bewildering. However, although this will eventually let you unlock everything over a long enough time period, the auto-assign applies a soldier's average grade to the best section, not where their speciality may lie. You'll get guys that have marked special skills and the system will take note of that, but say you exfiltrate someone with a B in R&D, two Cs in Intel and the rest Es. The auto option will throw him in Intel because his average would be around the middle of the grading metric, rather than where his B stat would have him perform best. Every time you journey back to Mother Base or complete a string of Side-Ops, dive into your Staff Management and make sure everyone's where they need to be. You'll be surprised how many basic items are locked away behind levels 8-10 of the respective struts, and if you're left in the field without something like a silenced pistol because of mis-managed soldiers, you've only yourself to blame.