Assuming you have all sidequests etc completed. I'm thinking of:
* take and complete 16 battle and GC lv.40-45 levequests (it's max allowed) on a class which you want to level first. Turn them on HW launch day and you'll probably instantly get half level XP.
* take and complete 6 Ixali quests, turn them on later for a a good XP chunk for your lv.50 crafting/gathering class.
* cap soldiery (in case if it'll be converted to poetics), GC seals (for GC rank up), possibly Hunt seals (for new vanity gear if there'll be any) and Wolf Marks.
* buy or spiritbond crafting/gathering materia for new lv.60 gear.
* craft or buy lv.25-40 gear for new jobs.
* reserve around 5 mln gil for new HW vanity gear or minions if you need those.
* stock ventures for leveling retainers or for new exlorations.
* clear your inventory, new main scenario missions will likely reward with V materia and other valuable items and you'll not want to miss them.
Any other ideas?