many players like to use Ice or Shock Elements. Ice slows your enemy movement by 50% and reduces their attack by 25% while Shock increases the damage you do by 12.5% and stacks four times for +50% total damage. the Ice lasts 3 seconds after you stop hitting your opponent, and Shock lasts 5 seconds.
Eternal Items are powerful, because their Item Quality is +50% and all affixes except Crystal are doubled (Crystal affixes are already tripled), but many Crystals can’t be used on them. Legend Item affixes aren’t doubled, and Item Quality can only go up to +25%, which makes them less powerful, but you can use all Crystals on them. Power versus Versatility. here are the Crystals that can’t be used on Eternal Items. Mythic Items are made using a recipe of 4 Myth Stones to create a Mythic affix on an item.
eventually you will have enough Crystals to make a PVP Build that is only for fighting in the Battle Arena, and a Build for Farming in PVE, and later another Build for Climbing Floors (if you are interested in climbing floors).
do a search on PVP Builds to get an idea of affixes that work well in PVP, because there are some affixes that work better in PVP, and others that work better in PVE.