Here are a few guidelines for people to assist them in any confusion! These are, of course, just examples of when I'd say people get things, if you'd allow someone something else earlier or later, that's a-okay. Athos is a bit of a special case, in that until Floor 4, he is limited to what I've listed, but after that you're a bit more free to give him what you'd feel he can have. Obviously, if you don't let Athos use Nosferatu, you wouldn't have to let him have it in the Dungeon.
Athos -- Floor 1: Eclipse, Heal Staff | Floor 2: Bolting | Floor 3: Purge, Restore Staff | Floor 4: First Rank Anima Books, Mend Staff | Floor 5: Sleep Staff | Floor 6: Second Rank Anima, Dark and Light Books | Floor 7: Aureolia and Forblaze
Benjamin -- Floor 1: Cure | Floor 2: Bombs (MT Damage), Fire, Quake (MT Magic) | Floor 3: Heal (Status Healing), Halves Water, Immune POIZN, Silence | Floor 4: Jumbo Bombs, Halves Fire, Charm Claw (Poison / Paralyze / Sleep / Blind / Confusion), Thunder, Life, White | Floor 5: Immunes Paralyze, Meteor (MT Wizard spell) | Floor 6: Mega Grenade, Halve Wind, Immune Sleep, Blind, Confusion, Flare, DRAGON CLAW | Floor 7: Immune Stone
Note: Ben can MT most of his spells for a damage penalty, the ones I listed are just automatically MT'ed, if I'm not mistaken.
Nate -- Floor 1 (Pixie: SP 6| Strong: Earth, Weak: Wind Dia (35% healing), Garu (20% Wind), Zio (20% Lightning) Maha Garu (Group Wind), Megido (25% Non Elemental)
Floor 2 (Genjo: 10 SP | Voids Mind/Nerve (Zan (20% Nonelemental) Media (40% Healing, MT), Holy Light (40% Light damage, MT)
Floor 3 (Aizen Myouou 14 SP: Voids Earth/Holy/Darkness (Hama (35% Holy ID), Suku and Maka Kaja (Speed and Magic doubling buffs), Holy Light, Maha Magnus (40% MT Earth))
Floor 5 (Shaka, 18 SP: Strong against all (Holy Light, Recarm (revival), Mafui (25% Silence), Hypnotic Wave (MT Sleep, 45%), Nirvana (50% Holy), Vile Thunderbolt (50% Lightning), Refresh Ring (Status healing)
SoM Casters: 4 Second is 1 Average Turn, spells take 2 seconds to cast.
SD3 Characters: Formchange 1 at Floor 3, Formchange 2 at Floor 6. Spellcasting depends on the spells themselves, 2 seconds is average I think?