A couple noob question

[Zeykes]

Relatively new player here, I started around when the game got the english language option. I'm currently rank 47 with Weapon Master and Dark Fencer mastered.
First off, to make it easier to answer my questions, here are some screens of the stuff I have currently:
Weapons:
Page 1
Page 2

Summons:
Page 2
Page 1 is just angel/archangel stuff +Wind Carbuncle

Characters:
Page 1
Page 2


And then the questions:
I'm wondering which element should I try to focus on (as in, which omega/magna should I farm for weapons/summon etc), and which SSR/SR characters in that element should I try to get? (Saving my crystals and premium draw tickets for any good draw events).

I'm very interested in the Sword Master class, is it any good? I think I read somewhere that the Warrior Creeds and trophy needed to unlock it comes from the extra stages in co-op, but which stage(s) is it specifically, and what are the requirements to get there? (I'm currently working my way through the hard stages as I've pretty much ignored co-op overall until recently).

And if Sword Master isn't any good, or isn't something I should bother working on yet, which classes would you recommend me to master? (Currently got 660 CP saved up).

What are plus marks and how do you get them? (the +xx on weapons/summons).

Best way to get Supreme Merits?

I noticed that mastered classes have class-specific skills obtainable via EMP (Extended Mastery Points). Are these worth saving up my points for, and if so, which? Or should I just spend EMP on the passive bonuses?


Questions with a line through them has been answered already (though if you feel you have something to add to the answers, feel free) 

Thanks in advance for any of the questions you are able to answer!

[teddoken]

1. swordmasters good if you have a good sword. sword effects are what makes the class. warrior creeds drop from any ex stage. just pick your poison. i prefer dark matter. just do every stage and you'll reach dark matter eventually.

2. stat bonuses. +1hp +5atk per bonus on weapons and summons. +1hp +3atk on characters.

3. events. bahamut drops gold certs from time to time.

4. depends. break lock is nice for hawkeye, and horizontal stance is nice for ogre, but don't bother buying skills for classes you aren't going to use. focus on the zenith perks before zenith skills.

[Zeykes]

Thank you for the quick response!

Would you consider either Lyst Sin (Vira's weapon) or Red Sun (fire katana form current event) good weapons for a Sword Master?

And which zenith perks should I prioritize? (got a star in ATK so far).

[teddoken]

i heard red sun is good since it gives multiattack rate+. lyst sin is pretty much just only good for break damage. here's a list of swords and their effects if you want to decide for yourself docs.google.com/spreadsheets/d/1Qn76lemsOMnK0EZnS4UIdcsKZ9vcj8GUD_KL61UPmxg/edit?usp=sharing

i like atk and hp. depending on your class, debuff rate+. people like using double attack+ too

[Zeykes]

Sweet, thanks again!

Edit: And if I were to go for Sword Master with Red Sun, I suppose I should focus on the fire element (at least for now).