Priority number 1
Cap and hold caps ! GLOPS is all about cap control. Winning GLOPS by pure damage alone happens very seldom.
Everybody should cap, doesnt matter if you play afv, td, lights or arty. Get your ass on the caps, cap it and then move away to a position where you can help defending caps or provide support to the guys that try to cap. Dont be that guy on in the top right corner sniping random targets the whole match and ignoring the caps.
Other stuff :
Only go for wild cards if you are near them. Dont spend a minute or two driving to a bunker wildcard and then 20 seconds extra to cap it. Thats valuable time doing damage wasted or capping.
Airstrikes/airplane wildcard are the exception, get them yourself or deny the other team the chance to use them.
For maximum payout in money and experience :
Go for caps, cap and hold them
Use commanders with high spotting range
Put binoculars on your mbt.
Track those you cant penetrate.
That will give you extra exp, money and victory points for capping, spotting and damage dealing. And you usually will be among the top 5.
Beware going hard for caps will put you in harms way. Learn to always have you front towards those that can hurt you the most. Learn the weakspots on other tanks. Facehugging an mbt with your mbt and theres other enemy vehicles arround? Then shot at soft targets that can move and hit you in the sides or back. If you are lucky the mbt your facehugging dont know where to shoot you.