Finish the Stormblood main scenario questline.
Have your Job's Level 70 Antiquated weapon (if discarded, buy it from a Calamity Salvager).
To make sure I'm giving you the best advice for your journey, let me know: Are you planning to do this or with a group ? Eureka
Use the Magia Board to change elements to increase damage and defense (/magiaauto).
Which are you starting in? (Anemos, Pagos, Pyros, or Hydatos) Finish the Stormblood main scenario questline
Complete the Weekly Eureka Challenge Log for massive XP.
Complete "They Call It Eureka" from Galiena in Rhalgar's Reach (X:9.8, Y:12.5). Eureka
Are you aiming just for (the armor/weapon looks) or for BiS (Best in Slot) stats ?