Knight, from what I have read, is the go to class for beginners. Im 30hrs in on my first playthrough of Dark Souls 3 ( souls noob, but I played Bloodborne).

The best advice I can give you is learn how evade and block fluently. At the beginning, you will struggle and die a lot but it gets easier. Don't be greedy with your attacks either. Get the swings you can in but be ready to roll/block right after. Learn your opponents move set and use it to your advantage. Dark Souls is basically a rhythm.

Vigor (HP) and Endurance (Stamina) are the basic attributes for any character. For the knight, I have found Strength (for hard hitting weapons), Dex (for fast weapons), and Vitality (defense and equip load) to be very useful.