Ammo Problem Tips
I struggled with the early game, until I got my first Gewher 98. That gun is a workhorse. Put a silencer on it and you can finish some maps without initiating combat even once, just take out each enemy from a distance with a sniper.
Mouse or Fox work well for this since they get good bonuses for it. You can also spec your own merc to be a stealthy marksman as well.
Other than that, burst fire is a noob trap, especially the heavy machine gun. I have literally never used it once. Sniper rifles are much more ammo efficient and once you put a few good mods on your rifles, you can pretty reliably head shot an enemy from long distance.
My Fox has literally never missed a single headshot for opening a battle, especially using the Dragunov or M24. Just put a bipod on your rifle and go prone, the accuracy bonus is insane. I’m pretty sure you can hit 100% accuracy in this game, even though they don’t show the actual numbers.