What do you think are the most important skills to have for heavy, medium & light tanks?

I did read the rules & wiki although it seems outdated as it states to get Sixth Sense first, now it is just given away without the grind. I was curious about the one that lets you “hear” arty shots – is it worth it? I have a few crews that I should pick a new skill just unsure what would be most beneficial at this point.

Any and all responses are welcome.