I definitely suggest 21/15 for now (pure build). 18 strength would be hard for someone who is not familiar with turning into swings, etc.
Left swing: Best for close distance
Overhead: Best at medium distance and great for 2+ vs 1 person
right swing: Best for long distance.
Be mindful of which ways you are moving when you are fighting. Strafing is your friend.
Most of the time, strafe left if you want to right swing, strafe right if you want to left swing.
When fighting, it is good to strafe away from your opponent's swing direction.
When you left swing, turn right. When you right swing, turn left. It's up to you to decide whether you should turn and by how much, especially if you're strafing in that direction.
Beware of playing overly defensive. You can always bring your sword out and cancel whenever you want with a block. If you're overly defensive, you'll lose your pace against the opponent's offense.
Be mindful of your counters: Axes, Players on horses, and obviously people ganging up on you. If possible, try to be in an advantageous situation, and simply avoid these people if you don't feel confident.
In group fights, you want to use overheads primarily, and some left swings. If you use a short 1her, use left swings primarily, then overheads. It is a nice strategy to hold your swing until you can time a simultaneous swing with a teammate or at your opponent's back.
If you want practice, try going to the duel server for around 10 minutes before going to battle mode. Be aware of your mistakes and successful tactics while fighting.
