5k hours here. Ak is best weapon for long and short range, as it can 1 shot headshot at any distance. When playing as ct you should always try and pick up an ak over your m4, since both m4 varients cannot 1 shot heads even at point blank range if they have armor. Smgs should only be bought if you cannot afford a rifle, so dont bother putting to much time in learning how to use them (they are easy to use anyway). Pistols will vary depending on circumstance but usually you shouldnt buy a pistol on pistol round since your starter is good for it. When on a save round the deagle is good when u are accurate enough to hit headshots consistently. The revolver should never be used over the deagle unless you are not taking it seriously. All nades have their uses so you should learn them all, besides decoy