Quick Recommendations

A new player will likely benefit more from a magic-focused selection, since there are a number of highly accessible 5* magic damage costumes (pub recruits, free +5s). Just keep in mind that you can't use the monthly selective upgrade on costumes you don't own!

The Options

A new player will get the most value out of these tickets by sticking to the first set of costumes here. These will help the most when it comes to clearing the story and Evil Castle content.

Type	Portrait	Character	Costume	Purpose	Min	-1SP	Ideal	Notes
Core Supports (Most Important)					Min	-1SP	Ideal
Universal		Diana	Adventurer of the Unknown	Buff property damage	+0	+3	+5	The most valuable support when you have elemental advantage. Unless you're in a situation where you don't have elemental advantage, this is the best character to spend your upgrades on. Used 99.9% of the time in Fiend Hunt and better than 50% on Guild Raids. Pub recruitable.
Magic		Helena	B-Rank Idol	Buff Magic ATK + crit rate	+2	+3	+5	This is your premiere magic support for general content, she's an upgrade to the 4* Elpis. For Fiend Hunt and Guild raid, she's pretty much been replaced by Granadair. 50% crit rate at +5.
Magic		Levia	Track and Field Captain	Chains + Magic Vulnerability	+0	+1	+4	One of the top magic supports for general content. For Fiend Hunt and Guild Raid, she's used infrequently when fire doesn't have the advantage. The main target receives a stronger vulnerability debuff. Vulnerability potency increases at +2 and +4.
Physical		Lathel	Homunculus	Buff ATK	+1	+3	+5	The highest ATK buff in the game, but only for the first 2 turns. For the remaining turns, the potency is reduced to about half and can be kept up full time at +5. For general content, you're more likely to use Dark Saintess Liberta because she also buffs crit rate. He's meta for Last Night and one of the more commonly used supports in Fiend Hunt and, to a lesser extent, Guild Raid.
Physical		Rafina	Game Club	Chains + Physical Vulnerability	+0	+1	+4	Physical counterpart to Track and Field Captain Levia. Only worth considering if you lucked into a strong large AoE physical costume like Sacred Justia. She has limited use when water doesn't have the advantage for Fiend Hunt. Vulnerability potency increases at +2 and +4.

This is the second most valuable set of costumes in the pool. They're primarily used in Fiend Hunt and Guild Raid, so they won't help much for clearing story content.

Type	Portrait	Character	Costume	Purpose	Min	-1SP	Ideal	Notes
Intermediate Selections					Min	-1SP	Ideal
Universal		Zenith	Robin Hood	Chains + Concentrated Fire + Vulnerability	+0	+3	+3	Upgrade to the 3* Rigenette. Concentrated fire is a taunt effect that helps characters reach enemies they wouldn't normally be able to, either by positioning or their targeting type. This is one of the more frequently used supports for Fiend Hunt. Once you get a single copy, the other costumes in this group are higher priority for further upgrades. Costs 0SP at +3 with potentials.
Universal		Refithea	The Gluttonous	Crit damage + damage reduction aura	+0	+1	+5	She's mandatory for Fiend Hunt and Guild Raid, but you'll never use her outside of her field ability if you're missing her Pure White Blessing costume. Crit damage buff potency caps at +3, SP recovery increases at +4, and damage reduction increases at +5. Pub recruitable.
Magic		Seir	New Hire	Stacking damage buff when she's hit	+0	--	+5	This is a strong but niche late game pick if you have the other supports maxed out. She's very rarely used outside of Fiend Hunt and Guild Raid.

These are the only damage costumes in the pool. The first two are usable with just the one costume, the other two require their other costumes to be useful. All of the costumes in the previous two groups are more important than these. You are better off getting an extra copy of a support costume than take a single copy of these.

Type	Portrait	Character	Costume	Purpose	Min	-1SP	Ideal	Notes
Damage Costumes					Min	-1SP	Ideal
Magic		Loen	Last Hope	Raw damage	+0	--	+5	Her damage and 3-turn cooldown makes her useful even without her other costumes. Very similar to Maid Name R Liatris, but without a conditional. She's a common pick for Fiend Hunt and for clearing rooms.
Magic		Venaka	Wind Dancer	Decent damage + increases wind damage taken	+0	+1	+5	She's a very common pick for Fiend Hunt and pairs well with the free Summer Vacation Dalvi costume. Vulnerability potency increases at +3. Pub recruitable.
Physical		Ventana	Comeback Idol	Self ATK buff + pure damage	+3	--	+5	She's a single target specialist, which has limited use to a new player, and not very useful with just the one costume. Very strong for Last Night, but there are better choices. ATK buff potency increases at +3.
Physical		Rubia	The Empress of the Ocean	Chains + DEF reduction	+0	+3		Damage is kinda mid. She's mostly used in Mirror Wars for the DEF reduction. She can also be used as a chainer in Last Night, but I'd skip grabbing her purely for that purpose because she'd only hold a temporary position until you'd get one of the better costumes.