Zwei frames weapons and armors will be the best to equip before getting your end game set which is the chaos set. Chaos materials like Quartz core (chaos), Material core (chaos) and Astral core (chaos) are able to buy in the Auction House in Bloody Ice. But if you would like to farm for it, you need to go to Abandoned City (Hardest dungeon) and break some chaos equipments drop in there.
Zwei weapons can be farmed in Chaos Arena lv.6 while Zwei armors in Maquinas Outpost (Another hard dungeon).
Lastly, you need Unique elements: combination of rare element and basic element. Rare element can be farmed by doing the daily quest of B3F (Hard dungeon) which you need to ask help. Basic element are the fix reward from redeem system. Another way to obtain Rare element is by completing 30 Dungeon points (DP) and convert it to a Rare element in Port Lux DP NPC Peticia.