But Mary, what line should I go for as beginner?

Right, the tanks as such. Many more experienced players would recommend the Russian tanks. And I agree with them so far in that. But I would never recommend a beginner to buy a premium tier 8 tank before the one reaches the tier and have had some battles on the tier first. As for me, I grew up into the game myself through the heavy lines, KV-1S/KV-85, IS-3 on tier 8. And I recommend myself to you as a beginner to go the same way. The angled plates on the IS-3 makes it good facing the enemy, as long as you try to hide your lower glacis in that tank.