Note: if you don't want to invest into Ascended Dragon's stat pieces, Exotics from the Trading Post will do just fine. The trinkets are relatively cheap, here's a list of them from the official wiki.
Second set: you may have noticed a Focus on the second set, this one's for the tryhards. While Elementalists can't swap weapons in combat, they can still stack Bloodlust on random PvE mobs before fights using the second set then switch back to the first set once they're ready to PvP. The Bloodlust stacks will remain active without the need to sacrifice a sigil slot on the PvP set. It's enough to put 1 weapon into the second set as they'll inherit the missing one from the main set. If you have no intention to stack Bloodlust before fights then you don't need the 2nd set! It's not mandatory.