

They gain bonuses for each Legendary / Ancient item equipped. In contrast with previous, they rely on your character not having any class set items equipped. Legacy of Nightmares (LoN) or Legacy of Dreams (LoD) builds.

Once you complete the set, you aim for additional items that affect the same skill or generally improve your character. Sets have some ridiculous modificators to damage of some skills, like "Skill X now deals 10000% more damage".

Your goal is to complete full set of character specific gear. In current game version there are two types of endgame gear: Top players manage to complete GR150, for novice players - it's good to aim into GR90-100. If you want to play endgame, you will probably want to build your character being able to complete high levels of Greater Rifts. You can complete the game with any items. If you just want to play main story, don't bother looking for the best gear.
