There's no "the best shielder build", it depends on your style, though personally I would go for 21-18.
Level: 30
Health Points: 66
Weapon Proficiency Points: 4
Strength: 21
Agility: 18
One Handed: 111
Ironflesh: 5
Power Strike: 7
Shield: 5
Athletics: 6
ANyway, balanced build liek 21-18 or 18-21 always are okay, no matter which class you play.
I want use my balanced champion sword!!
No need to loom items by yourself, you can buy any +3 item for 2 loom points and 0-200 k gold on the marketplace.
If you do not mind dying to 1-2 unblocked hits, I have a nice build for you. I would recommend to use light armor (leather etc.), an Elite Cav Shield or a Buckler, and a Blunt or Pierce weapon to make use of the high AGI this has:
LVL 30
STR 15
AGI 24
Skills converted: 8
PS: 5
Shield: 8
Athl: 8
WM: 2
1h: 123
Not for the knight in shiny armor, but nice for the fast moving skrimisher or backstabber.