Yo, allow me to put my sheet again… 
From my point of view…
1. Your early squad composition
Mainly filled with high rarity Caster and Sniper
If i were you, I will definitely prioritize 1 or 2 ops, NOT 3 or even more, yet. Seriously… NO.
By choosing the most (available) needed and usefulness, In this case
-Schwarz and Exia for single target.
-W or Meteorite for AoE. (pick one in this case).
Future (possible) target
(if the previous priority is lower tier, now is time for higher rarity to be raised, or maybe getting lower rarity BUT with also high impact on usage) =
-5* ST: Platinum or Blue Poison for general usage.
-4* ST: May, for utility
Skip those wide ranged sniper, GET your basic first.
Don’t go for ANY archetype if your basic is not yet fulfilled.
This very same rule is applied for ANY OTHER ROLES.
For AoE since we only need 1 for general usage, then only Meteorite and W are worth to be prioritized. Both are okay
BUT remember, you are still starting, chose 1 only. Save the rest of mentioned ops above for later.
No need to rush,
as long as you stay in this path, your stepping-stone will be in shape before you even realize it.
Caster
This time, it’s easier as you have some big names, and you can forget the rest.
4 top priorities for Arts damage dealer for many days ahead, only this 4, rest are not needed anymore. Stop overthinking.
1.Eyja as the queen, get M3 on her S2 and S3 asap.
Having ONLY her will carry you far enough as she is so broken.
2.Ange as multipurpose and arts key combo
3.Suzuran as AoE slower and debuff arts combo S2/S3 M3.
4.Ceobe as Boss slayer
Ifrit can be skipped but if you want to try her
archetype, do it later, same for Leizi.
Worthy late game true debuffer in this case are only Pramanix or Shamare, choose 1, but still skippable.
No other slower needed beside Suzuran, for a long term.
Skip other lower rarity if they only offers damage and little to no notable utility.
Except one, Beeswax. Save one spot for her, she is a caster on paper, but basically she is a “Ranged tanker”, she will shine in your late game.
Same rules for Thorn, he is not a guard imo, he’s just a “Ground sniper” also Lady Saria, she is a “Ground Medic”.
No further explanation needed, get it or not, get those 4 to good level after E2, example 20~50 is enough.
NO need to get max lvl, yet. NO need.
But beware they will put an evil smile on your face once you get them.
That would be all for your ranged utility and damage dealer. Having them properly raised will greatly step up your game.
Because your ranged unit is such an overkill already, do the same for your melee ops, the same rules can be applied, by prioritizing 1 or 2 of their basic role or archetype. Remember, step by step, NO need to rush.
Starting on your Vanguard, this one role should be special case, lots of room needed.
Myrtle and Elysium, E2 up to lvl 20 is enough, S1 M3.
Siege, durable and high damage. Best generalist.
Texas, get 2DP early, stun and damage, low def, its okay as 2nd best. Forget scavenger, she should be skipped.
Zima, buffer of other vanguard, tanky type like Courier.
Zima can be brought to late game, not for courier.
Save 1 spot DP on kill Vanguard, even Vigna could bring you far. Bagpipe is the final target, get her and forget the rest DP on kill Vanguard.
Might be continued or terminated upon request.