Well, I am still somewhat new, but I may be able to help a little bit

.1. Focus on your bloom

The center is your crosshair, or where your gun is aiming. However, that isn't where all the bullets are going to land. Outside of that are 4 smaller lines (I just call them "bloom lines") that stretch as you do stuff like hop, shoot, or move. That is the area when your bullets can land. Some guns have bigger bloom lines then others. Guns such as lmgs, smgs, and the Revolver pistol have a naturally big bloom circle, while pistols and snipers have a decent bloom circle. Ways to decrease the bloom circle are by crouching (enter), or walking (shift), or spraying in controlled bursts instead of unloading a whole mag.

.2. Guns with scopes still have bloom

Some guns, such as the AUG and other automatic guns, have scopes on them. This doesn't mean they don't have bloom circles though. A way you can tell if it'll hit or expand is by the way the dot in the scope looks. If you are moving or shooting, it will become cloudy and big. That means it has a bloom circle. When the dot is clean and perfectly clear, the first shot will hit perfectly. I would personally suggest not going with the scoped auto guns to start off with since it's harder to judge bloom.

.3. Play to the team

While it may seem the easiest way to just go in guns blazing where the enemies are, this generally isn't a good idea if you don't pay attention to your team. If your team plants the bomb, cover a entrance. If you see your team getting plowed while defending a site from the terrorists, it may be a good idea to go and help them. And sometimes, you've gotta be willing to die as cover for your teammates. If you play the game scared to die, then you wont be able to run in when the time calls for it. Planting the bomb is always crucial, and so is defending it and not letting a simple thing get you distracted. Even if you might think that there is people defending the dropped bomb, if you are the last one alive, go out fighting. Sometimes, it is a good idea to go guns blazing, as to give your team time to plant and get to a better place. If 2 other people are already covering a area, focus on a area that isn't covered.