I would play breakout if you want to improve your skills. Use your shotgun most of the time and if someone is out of range, switch to your pistol. Don't be a kamikaze rushing forward with your weapon firing like crazy. Get good at throwing grenades, a lot of people don't give them enough attention. Don't pick up any other weapons on the map until you are good at using the weapons you spawn with.

To keep from dying, use radar, sliding, jumping and boosting to evade the enemy. If you want to get really good at this, don't even try to kill the enemy, just get close to one and see how long you can survive by jumping and boosting. Your best bet as a noob is to just stick next to somebody else and team shoot the enemy or kill the guy who kills your teammate.

When you are playing and you take several shots, get behind a barrier and wait for your shields to come back up. If you are sprinting, your shields will not regenerate, so stop and hide. Don't be too ashamed to camp and ambush people. If your enemy is better than you, that might be the only way you can kill them.

Most importantly, get a headset and find other friends with mics so you can communicate and give each other callouts.