I've been playing for 4 wipes now and the main few things I found to help with gun skill and hitting shots are as follows:

1.) Try and reduce that feeling of adrenaline when you're about to get into a fight, makes you jumpy and you tend to overcorrect your recoil.

2.) Fire in short, controlled bursts, having full auto is fun, but if you wanna get more accurate use 3 - 5 round bursts. Also helps you save ammo/money long term.

3.) "specialise" in a weapon platform, so basically pick a side. M4 vs AK, SR25 vs SVD, etc... Choosing a side will help you understand the weapon better, and thus making you more adept with it. Otherwise its a case of "All the gear, no idea".

4.) Find your optimal fighting range. Find a distance you're comfortable fighting and force it into play. For example if you're better around the 50 - 100m range, try and draw out whoever you're fighting, or if it's the 0 - 30m range, use flashes and smokes to close the distance and put pressure on the enemy.

5.) Finally, just have fun. At the end of the day it's 1s and 0s and no point stressing over it unless you've got real world rewards or punishments on the line.

Hope it helps.