Skill level necessary to clear HW MSQ content

[MrThinker]

For someone new to EX, which one do you recommend to start with, Garuda, Leviathan, Ultima Weapon or Thornmarch?

I won't start any of them until I can both consistently run these story primals and fix my gear problems in full.

Garuda, as the 1st released Extreme trial, is by definition the easiest, as you can vastly outgear the fight's minimum required item level and thus fail quite a few mechanics before it becomes unrecoverable.

However, as has been said before, the mechanical complexity and punishments of Extreme trials is VASTLY greater than any main-scenario required instanced duty. Getting used to what is required for Extreme will make you realise that most MSQ content is not that difficult in comparison. Not that I am against self-improvement, but if reaching the end of the main-scenario as it is right now is your goal, simply focusing on it will teach you the mechanics you need to recognize.

Also the fact that because they are both 'optional' and 'not in a roulette because the average player wont be able to complete it' (except one, where if people get an extreme trial in that roulette, will most likely abandon ship), q-ing for it directly via duty finder will very likely be an exercise in futility. You will need to set up a Party Finder detailing what you plan to do in the content and hope that some like-minded or helpful individuals will join.

EDIT: Correction, Ultima Weapon is apparently the 1st Extreme.

EDIT2: Also, there are no Extreme trials that are mandatory to complete to progress the story. Garuda, Titan and Ifrit Extreme have a small side story chain associated with them, and some of the info of that chain is later reflected in the story, but is by no means mandatory.