This page on the oblivion wiki has a lot of your answers, including a list of all possible followers that you can get (even quest related ones). Keep in mind that for many of these characters, if they die their quest will fail, so its up to you to decide if you prefer a follower or the quest reward.
It also addresses the issues of equipping your followers and managing them:
One limitation of NPC followers is that they generally have mediocre equipment. And since NPCs never repair their equipment, it can become useless after a few fights. Most followers will pick up the best quality weapon available in the area when they start attacking, so all you need to do is drop a good weapon in front of them at the start of a fight.
You can add other items to your followers' inventory by reverse pickpocketing , but only if the item is zero weight . A few zero weight clothing items are available, and can be made more useful with enchantments. The best way to acquire armor, however, is by taking advantage of the permanent bound items glitch ; a zero-weight version of any Bound Armor or weapon can be created this way. Enchant armor with effects like Fortify Attribute or Shield ; add effects like Shock Damage or Absorb Health to a weapon. Your ally should automatically switch to the best quality item in their inventory, and will therefore equip your enchanted item. If not, fast travel or entering a new cell may be necessary.
Maintaining a large entourage may cause problems in that followers can hit each other in combat and end up fighting one another.
- Due to the nature of their attacks, followers with ranged, or area of effect attacks appear to be particularly vulnerable to this sort of behavior. Like the player however, melee-based Followers must strike each other 3 times before turning hostile to one another.
- 100% Chameleon will prevent this behavior, as Followers are incapable of retaliating against invisible attackers.
- PC users may also use the Console to increase the Disposition between Followers.
If you want to teach followers spells, the only way to do so is through the console.