I'm really missing something here. I can't get past the 5th level of the tutorial and I feel like an idiot. There's three skeles and I can kill two of them but by the third I'm down to the Old Knife and no shield so I always get killed. I can't figure this out. Also what's with this thing where it looks like you can upgrade weapons?
Ah, that's a tricky one! :) every monster you defeat should free up another card, either armor or a sword. And with each freed card you can defeat another monster. So it's a case of finding the right order. Hope that helps!
As for the +1/-1 buttons, those just show how the card would change if you'd upgrade it. You can't upgrade the card there, just preview it.