I recommend these skills + last one of your choosing. They complement and buff each other.
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Since I started using them the game was too easy to be exciting but it helps with grinding.
You get one slot empty for the skill of your choosing, but I like to pick zombie eater as the last one just to have more enemies to kill
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Sage time makes you faster and, from damage perspective, all hits to the body are treated as if you hit the head or weak point (Doesn't increase the points though).
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Remission 3 to make it faster to heal and reload the buff easier.
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Recovery rate 3 to heal you and the girl all up in one healing.
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Steel Body (+100HP) + Buffed sage time (+50%) = 300 HP which helps you to refill your vitality really fast just for taking damage by zombies. I literally let the 3 or 4 last zombies bite me a few times so I can just gather vitality to extend the buff

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Revolver + Sage time buffed = a single hit to the body of a zombie is equal to blowing his head up on very hard just like on the gif I posted earlier. In fact I think I had only 2 or 3 headshots back there, the rest was only hits to the body that look like a headshot.
I don't get more vitality since 3 is enough, and if I see it somewhere on the way but I'm full then I eather heal for the sake of extending the buff or just go forward. I can always come back for it if I need it if I'm close and if I'm far I usually have already recovered enough from the damage received.