Neutral rune is always the fastest way to climb up the current ladder due to its fast-paced and consistent playstyle whether you're going first or second. Aggro Blood is faster than rune, but suffers greatly going 2nd. Mid shadow is slower than both of them, but doesn't suffer facing heal-intensive decks like ramp dragon and elana haven.
Well it's pretty much up to your comfort which you would run, since i don't know what you've been running against in the ladder, but those 3 decks are what's dominating the current ladder meta rn. I'd recommend waiting for the nerfs to drop first though.