I'm sorry i can't help much but the usual "playing and practicing makes you a better player". You can do tutorials to learn about game's mechanics. Can't tell you much about ships and aviations but for tanks, at least in start, choosing right faction may help. I noticed that german tanks in the beginning were super slow in moving forward/left/right and turning the turret. Could be just me, other people can approve/disapprovethis statement.
Practice a lot and dont rage thats my tip