A build that's currently popular is the Bushido Mage (aka the "Bok Mage"). Its more of a hybrid than a true caster, but lots of fun none the less.
Usually has the following skills:
110 Magery
120 Eval Intel
120 Bushido
120 Parrying
120 Resist Spells
120 Swordsmanship
060 Tactics
Template uses a Bokuto for Nerve Strike special move. Nerve strike damage scales with Bushido. Only 60 tactics needed in order to perform nerve strike. Need to be able to find atleast 40 to 60 skill points from items. Generally only 110 Magery needed since you're not really performing any 8th circle spells, but suggested to bump up to 120 Magery if you have the skill points available. Need atleast 80 dex after using potions, although probably a bit higher to have a buffer for when you get cursed.
Others might have some of their own variations on the build (I'm certainly not an expert in PVP), but that should give you the general break down. Here's a YouTube guide on the build that I suggest having a look at:
(346) The Bok Mage Build - YouTube
Good luck!