Here is my advice. Take a step back to a tier 1 or 2 tank. They are all basically the same: No armor to speak of, guns that can pen eachother decently (except the ultra armored H35 variants), about equally fast, etc. You see less maps, you can figure out ways to exploit certain things on maps (I am looking at you himmelsdorf). You learn the importance of flanking, staying the hell out of the firing lines of TD's (which will stay with you for life), understand when a push can help win a flank and when it is suicidal (something I have yet to learn with my 17k battles).
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Llwellyn, I like Possessed Freak's advice.
Basically, you're not having fun in the game and are on the verge of giving up on it for whatever reasons (feeling that you're not good as you expect you should be, etc.). I think taking a step back to the lower tiers is good as it resets things for you.
If you have too, start a new account (even if it's only for temporary use) and start real fresh (leaving the past behind -- at least for a while). I think you need to find where the game is fun for you again. That's the reason most of us are playing after-all. Find that fun sweet spot for yourself and enjoy the game just for playing. You don't need to be playing high tiers if it's not enjoyable for you.
Aside from relearning the basics again, going back to tier ones and twos can be a lot of fun anyway. I've recently gone back to help a friend who just started the game and I'm finding a lot of joy revisiting tanks I used to think were bad. It turns out, I was just bad when I drove them as a newb ... LOL!
To each his own, but for me the T1 and the LTractor are a blast to play with their fast firing machine guns that have multiple bursts (make sure to reaim between bursts). The T1 has better mobility, but it's reload between canisters is slow (about 10 seconds). The LTractor is slow but its reload is only about 3 seconds.
Here's some tips I've learned for the lower tiers that may be useful:
Since lower tiers have almost no armor, always stay close to hard cover so that you have a safe place to hide from enemy fire (especially when you're reloading your gun). Be very careful if you have to go out in the open.
Use the "C" to reload whenever you have a partially expended canister and have cover and time to reload.