Each of your equipped items contribute equally to your average ilvl, so improving your accessories is generally the cheapest way if you are only interesed in increasing your ilvl - and assuming all your gear had the same ilvl at start.

The left-side gear is however the one contributing most to your actual combat ability, with your weapon the most important part, followed by chest and leg items.


Probably a bit too late for you now, but remember that you can use Centurio Clan seals to buy i330 gear and upgrade it to i340. If you have been doing hunts in advance you can thus easily get i340 gear the very moment you reach level 70 which should open up much of the level 70 content.