If you want to use the Mastery Chain system
efficiently, you will want to put all PvM characters on one account so that they can share all experience they accumulate in PvM. After that your only decisions are really if you want multiple characters or ONE character with multiple echoes. The main things to consider when making this choice is the increasing Echo cost when unlocking multiple echoes, the cost to get a new PvM character up and running (Skill Orbs, Skill Scrolls, etc...), and which characters will need which tomes/aspects and whether or not you may have to level certain tomes/aspects more than once.
In general echoes will be the more convenient option as long as you can work around the echo cooldown, however this option will be MUCH more expensive once you've unlocked a few echoes due to their increasing cost.
Also, make sure you check out the outlands rules page (
https://uooutlands.com/rules/) regarding how many accounts you can have.
