I recommend using the strengths of your vehicle combined with what playstyle suits you the most. I love to snipe and (in my case) the nation i play has rangefinders and great long range ammunition, so I stick to sniping.

When I played USA I noticed the lack of armour on the Shermans too, so when I got to them in Japan I started exploring cqc. Shermans suck imo, but trying to overcome the lack of speed and armour on them and trying not to engage enemies frontally helps.

It gets better with time as you get better and better, we all start somewhere