If you're just zerg surfing, then you can just focus on the good old Haunting Curse -> Crushing Shock -> Endless Fury -> Crystal Frags combo. The rest is self buff and defense. Hardened Ward, Harness Magicka, Healing Ward is your shield stack. Streak and Boundless Storm for mobility. Dark Conversion for when you're safe and need more magicka. Power Surge and Inner Light if you don't want to bother drinking potions for the Major Sorcery and Prophesy buffs.
Gear-wise, get some Shacklebreaker and Seducer to start off. Both are crafted sets, so no farming necessary. Just get a friend or guild mate to make them if you don't have a crafter yourself yet. Then you can farm Lich or Amberplasm, which should replace Seducer. You could also swap Shacklebreaker for something else like Julianos if you really want, but I think the extra stamina regen and max stam helps. You just need 1 monster set piece. Anything that gives magicka, like Grothdarr, Ilambris. You could choose one of the above sets and pair it with 3 Willpower Jewelry and the Infernal Guardian monster set also if you want to shoot mortars at people from within your zerg.
I run Shacklebreaker+Lich in BGs to good effect with most of the skills I listed above.