There are couple of options/advices I could give you.
If you're going with high AP regeneration, you can use pistols and spam shots or use machineguns and burst. (In this cases INT> LK)
Or you can go with aimed shots with pistols (for example head or groin) shift + number to aim (this will drain more AP and make your effective range smaller) in case of aimed shots (LK>INT)
I talk about INT and LK because INT is related to general critical chances and LK is related to aimed critical chances. Gun skill is something that effects your range and number of successful shots in general. You put points into this at first. Until 150% you will be bad at shooting, 150-200, you'll be much better, above 200% your char properly knows how to shoot
Generally, if you aren't making a build for critical shots its not healthy to just stay in one place and shoot. Run around, use cover, wait till your AP regenerates.
All in all, I presume you don't have experience from another Fonline servers, but in time you'll learn a trick or two. It takes practice. Also in this game its very healthy to have a team/partner instead of going alone.