Unlocks are the one-off account gates: an allied race you want to play, heritage armour, a zone that needs a questline finished, a delve tier, or the dungeon portals that save a flight every week. None of them are hard — they are all just long.
Because unlocks are account-wide, this is the category with the longest payback: done once, every future character benefits.
Account-wide, done once
Allied race and heritage armour unlocks apply to your whole account. Teleports and zone access apply to the character they are earned on, which matters if you are planning a new main.