Gajeel joins Fairy Tail after the Paradise Tower arc, along with Juvia, who had been helping Natsu's team since the Phantom Lord arc finished.
'Like' is a bit of a stretch for Gajeel, the most I'd say is he feels an obligation towards her due to the time when he attacked the guild, severely injuring Levi, Jet and Droy.
Episode 130 is when she officially joins
27 is part of it so maybe 26,27,28. try those.
233 and joins the crew in episode 322 after Robin forces him to by grabbing his nuts
First one had to become an apprentice, after that when they had learned the trade they became a member of that crafting guild. A guild is like a modern day Union.
Tuesdays
Show it to Chatot in the guild.
You must beat the game once by battling dialga, then defeat the guild members and graduate from the guild. Then the episode will be unlocked.
you have to graduate from the guild
Sai joins team 7 in Naruto shippunden episode 34
Sasuke joins Orochimaru in the end of episode 109 but everyone(except Sakura) finds out in episode 110