Magic Stun

Ice bolt and Lightning bolt stun time can be used to your advantage in different situations.
For example, using it after a combo is a good idea if you don't have a kite shield yet and your getting too much damage defending against X monster.

The stun can also be used to skill-lock an enemy if you look at the previously linked ice-crit gif that icebolt would've locked the skeleton on counter state if it wasnt a crit, making the wolf stay in counter untill hit.
Skill Lock can be very usefull, if you stun-lock a mob on counter you can windmill the rest of the room without getting any aggro.

Advanced Tactics

After you understand the basics of combat you can go ahead and try the following.

N+1: This means adding one hit to your combo , doing 3 hits with a 2 hit weapon, and doing 4 hits with a 3 hit weapon.
Basically, you have to wait a bit after doing the first hit(with a 2hit weapon)
Or wait a bit after first and second hit(with a 3hit weapon)
Depending on weapon speed and hits, the time you have to wait is different.
The only way to learn this is by watching someone do it and practicing.

1+WM: Doing a windmill after a single attack is useful when theres many mobs around, is also the best way to kill imps and flying swords, since a windmill will always make them cast, you can just keep doing 1+WM on them untill they die.
Just press WM right when you click to attack, you can also do 1+1+WM mabinogi money, which means you'll be doing the first two hits of N+1 and then WM.

Switching Weapons while comboing: This can be usefull if you have a 2handed in auxiliary and shield+weapon on primary. If you want the use the 2 handed because of damage and you want to use defense with a shield, you can start the combo with the 2handed switch quickly by pressint TAB and finish combo with wep+shield, you can also switch back to the 2handed right after you defend yourself without having to hit first.

You can also do 1>switch+mill, where you hit the mob switch quickly and windmill.

1+Defense: Useful if you just want the enemy to always directly attack you, instead of him wandering around or doing counter, etc.
Hit and do defense as soon as possible, depending on your lag you might need to walk back a bit or not at all.

WM Spam: Not really advanced since all you do is spam WM...  mabinogi moneybut it does requires some timing on multi aggro, can only be used against mobs with same speed as you or mobs that takes a while to stand up as snakes and spiders.