The background Warblers from S3 onwards are properly introduced in S4:

Kyle:  His twin sister is Aria. He is comes in S3 when Sebastian is captain. But is properly introduced in S4 titled Suddenly Seymour, where he talks about his audition for the warblers to his twin and mentions that he auditioned with a song from the musical Little Shop of Horrors. He crushes on Kitty when he meets her. He later becomes best friends with Skylar. His background story is that his parents don't care about him and Aria and they live with their older brother Connor.

Louis: He's the oldest of triplets. He's a junior in S3 but in S4 he's a senior, he's against Hunter's steroids. He goes against them and doesn't perform with Trent and his brothers. Louis is unlabeled.

Alex: He's the middle triplet. He's really nerdy and keeps to himself. He loves to sing but is really shy. He's introduced more in Suddenly Seymour at the Lima Bean where we see Louis trying to convince him to leave the Warblers for now. He's asexual

Jack: He's the youngest of the triplets. He's really out there. He's a party person. His best friend is Hunter. He's also bisexual and hooked up with Hunter a few times.

Barry: He's really geeky. a freshmen. Wants to stand out but is worried about messing up. He's Trent's little brother.

Henry: He's at Dalton and part of the warblers because of his father and uncle. He's the older cousin of Jane.

All the newbies are not mean. they are kind and inclusive. They don't bully anyone at all. They opinionated and disagree on many things but they aren't mean at all. and none of them are selfish at all.

The Warblers from S6 (Except Skylar who is in S4) are introduced in S5:

Adrian: He's Skylar's second in charge having been part of the group for a long time. He's a rich kid and at Dalton because he's dating a girl that isn't rich and his dad disapproves. His girlfriend is Unique.

Justin: He's best friends with Adrian. and helps him sneak out to his girlfriend. Justin is bisexual.

Jayden: is bisexual. He's part of the warbler council. and doesn't agree with Skylar's tactics of being captain and lets him know. he helps Skylar with the audition process

Phillip: He's part of the warbler council team. He always agrees with Skylar's ideas. He loves Lauren Zizes

And again these warblers are nice and kind. These Warblers are introduced properly in the episode after the Quarterback known as Prom, where they go to McKinley's prom as their dates.

Adrian-Unique

Justin- Tina

Jayden-Sugar

Phillip- Lauren

The Prom S5 ep is where Jake and Skylar come out as bisexual and start dating each other.