A popular choice for mages is the Apocalypse spell package that adds over 150 unique spells to the game that give a lot of strategy. There's also Phenderix Magic Evolved, which while not as complex as Apocalypse, is great for roleplaying characters due to adding several different archtypes (holy, earth, dark, wind, water, Ect.). Phenderix \also adds an archtype of blood spells that cost health to use. If you use Phenderix I would advise getting Apocalypse too since it has an "erase spell" spell. Otherwise your spellbook might get a bit clogged up with Phenederix's spells (there's 270, but most of them are pretty similar to eachother). A great mod for any replay is the Skyrim Monster Mod which adds tons of monsters to Skyrim. The only problem with it is A. I believe it replaces vanilla animals and B. some of the creatures it adds are lore breaking (people don't seem to like tricera tops in a game that has mammoths, yet nobody complained when he made a Balrog). I also hear that it can be a bit buggy, but then again, so can vanilla Skyrim.