When it's the time to move on?

Ph3lan: Hi CarelessOne!   Here is my two cents: I would go for a Tier VIII heavy tank as my first dip into higher tier matches. As some others have already pointed out above, heavies in general are a bit more forgiving compared to mediums which makes them a safer entry point in my opinion. Specifically I would go for the IS if you have the previous tanks researched. It is a very well rounded tank leading into one of the most popular tank lines in the game and aside from its gun handling there is not much going against it. Before buying it I would watch a couple of youtube videos about it, but more importantly I would watch a lot of replays with the tank to see how other already experienced players use it. If you go to wotreplays.com and search for IS replays filtering them according to xp/damage/kills you can find a lot of great replays. After that I would just start playing it. At first it is quite likely that you will perform worse than usual, but I wouldn't worry about it too much, just stick with it, try to do your best and have fun! This was the method I used when I was preparing to jump into a new Tier, and it worked quite well
  Good luck