Suika is a fast melee brawler with strong options at close and mid range. Her dial-A does huge damage, giving her an easy learning curve. Her basic combos, even without her dial-A, are fairly easy and she does pretty large damage even with j6a j6b and no followups. Her attacks are quite fast so mixups will take some practice, and her block pressure is fairly hard to perform for beginners since it relies on minimum height j6a. She also lacks a good graze attack (66c is her only graze attack), which can make the vs. Yuyuko and vs. Utsuho matchups hard. She is a powerful threat though and can punish mistakes from anywhere with a little practice.
Deck: 4x Oni Spirit Bomb, 4x Missing Power. Spiritual Strike Talismans are useful as she has no DP without losing Oni Spirit Bomb (requires level 3 Spectre: Dense) which is unacceptable. Fire Oni is generally seen as very useful. Other good cards include the rock throw 2-card (forget the name) and Throwing Atlas. Her spellcard variety is so-so. You only need 1 Spirit Bomb and can use the rest on spellcards.
#2: Meiling (China)
Meiling is basically a more well-rounded, shittier Marisa. She has more respectable zoning, a crossup game, and a graze attack, along with a good variety of spellcards. She has more deck variety than Suika, who basically has to run certain skillcards. She relies on fighting midscreen or fake pressuring in the corner, but has no ways to keep the enemy in blockstun and must rely on ghetto tricks. China is very dangerous in close, but it is fairly easy to guess her mixups. Her game mostly ends up being about punishing mistakes. Her vs. Iku matchup is extremely hard, but she is fairly decent against Yuyuko, Suwako, and Utsuho.
Deck: Most China decks ignore her 236 move entirely, as there are no good options for it. Her 214 attack has many good options, as does her 623. She has several invulnerable spellcards and should take at least one. Spiritual Strike Talisman is also a good idea.
An easy-to-play, melee-focused midrange character with good zoning, Iku is both incredibly strong and easy to play. She is Nick's main. Iku requires precise spacing which can only be learned with practice, but if Nick can learn it, anyone can. Iku has some tricky combo execution for random midscreen hits, but none of it is hard. Her midscreen dial-A followup is also somewhat hard to execute; Nick can't do it reliably. Iku has a lot of deck diversity, with only one card really being mandatory. She probably needs defensive cards, as she has a very weak close-range game despite her strong melee.
Deck: 4x Lightning Fish "Swimming Thunder Shot, 4x Spiritual Strike Talisman. Other than that, Iku can run a fairly wide variety of skill and spell cards. I see a lot of Lightning Sign: Elekiter Dragon Palace in high level play. Iku's 214 options are very diverse and it's worth playing with all of them. Thorn Sign: Thundercloud Strikeback is one of her best spellcards, too. I really like Veils Like Time, but I'm a weirdo.
She's super-China. She takes the strengths of China and magnifies them greatly, and her fullscreen laser gives her a way to punch through bullets and punish mistakes at any distance. Like China, she focuses heavily on doing big damage with random hits. It's up to you to land those random hits and confirm for big damage, though and while I personally find her execution easy, the rest of the group cannot confirm off of random jump melee (Nick being a notable exception and only with Iku). Because Marisa generates big damage off of any hit, she is much more dangerous than many of the other characters I've recommended (Suika does more, though). Marisa lacks a graze attack and must fight for midscreen position with her laser or 5c in most situations.
Deck: 4x Spiritual Strike Talisman. A lot of options here. Her default 214 is decent for combos and can be upgraded to be safer on block and allow for post-block mixups. Her 214 broomgun is also really good and is the most commonly used Marisa skillcard in high level play. Her default 623 is her only real graze attack, and it has startup graze which allows her some ghetto tricks. However, it does not have invincibility; it is not a real DP even at max level. She also has very good options for her 22 bombs and they can be used to control the map. Her spellcards vary widely and almost all are useful. For shits, 6c > Narrow Spark > Master Spark combos for all the lasers.
Considered by top players to be the second-worst character in the game, Utsuho deals massive damage off of most hits and has easy combos. I'd almost recommend her over Marisa, honestly, as her combos are much easier to learn. She is pretty slow though, and her sluggishness makes her hard to defend against. Fortunately, most of us are bad so her huge damage and huge bullet density are more powerful.
Deck: 4x Spiritual Strike Talisman, 4x Hell Geyser (also known as Gunflame). Shooting Star is also quite useful and Divine Raiment is helpful when you're getting rushed down. Rocket Dive is very popular for combos and shenanigans. She has very few useful spellcards.
Yuyuko (easy, strong bullets, easily rushed down)
Patchouli (powerful bullets, strong zoning, hard combos; more difficult, higher damage Yuyuko)