Build elementalist
wvw doesnt have a “meta” build it does have “meta” traits though. Gear set up is entirely up to you. Burst ele is possible, but be prepared to die alot.
Bad Elementalist
Most WvW ZERG elementalist run 0/0/0/6/6 with the last two points where you want, soldier gear, zerker trinket. That’s the safest build for a more support elementalist that will always be ready to give water field to the melee train. Its also the best build to start as its give you a lot of option to survive.
From there, as you get better build will change a lot depending on what you prefer. Some ppl are ready to sacrifice some of their defensive trait in Arcana for some sweet offensive trait in Fire to make you lava front and meteor shower hit hard and often.
Other buy rune of strenght and use sigil of battle to stack might for more dmg wihtout sacrificing your defensive trait.
Other go almost glass canon for massive burst on the ennemies, but you better be ready to get the help out because its easy to die.