You can heal effectively as any race, however you have to decide how you see yourself as a player. Do you want to play more casually or do you want to go for end-game raiding, pushing scores and aiming for the hardest content?
Playing casually you can choose whatever race you find most appealing, be that from looks, lore or amusement. Play what you will enjoy playing as and have fun whilst still being able to heal.
However, certain races are better suited for healing due to their bonuses to sustain, magicka sustain pool or spell/weapon damage.
Next list will be suitable for most common Magicka-based healing, so if you’re trying some fancy Stamina based build - logic will probably be the same but with reverted stats.
Breton Breton’s passives are powerful and extremely useful in PvE and PvP healing. As a Breton you have the best sustain compared to any other race. A good choice for pure healing on all levels from beginner to end game. You also have significantly increased defence against mag-specs in PvP.
Gift of Magnus - Increases your max Magicka by 2000.
Spell Attunement - Increases your Spell Resistance by 2310. This effect is doubles if you are affected with burning, chilled or concussed. Increases you Magicka recovery by 130.
Magica Mastery - Reduces the Magicka cost of your abilities by 7%.
High Elf High Elves have greater Spell/Weapon power than Bretons but what they gain in damage they lose out in sustain. They are still an excellent choice for PvE healing, and one of the best two races for DPS, which allows you to easily spec into Damage or make hybrid builds. The extra off-resource sustain gives Altmer more flexibility and defensibility in PvP.
Spell Recharge - When you activate a class ability, you restore 640 Magicka or Stamina whichever is lowest. This effect can occur once every 6 seconds. When you are using an ability with a channel or cast time, you take 5% less damage.
Syrabane's Boon - Increases your max Magicka by 2000.
Elemental Talent - Increases your Spell and Weapon damage by 258.
Dark Elf Very similar to High elf race, with more max Stamina instead of Stamina sustain. Excellent choice for PvE healing, hybrid builds and easy spec into DPS as BiS DPS race. The Flame resistance is really useful if you’re dealing with lots of ballista fire and oil in Cyrodiil.
Dynamic - Increases your max Magicka and max Stamina by 1910.
Resist Flame - Increases your Flame Resistance by 4620.
Ruination - Increases your Spell and Weapon damage by 258.
Argonian Argonians have slightly worse passives than Bretons overall, but still are a good choice for casual/mid level PvE healing. However, their sustain passive is anti-synergetic with Pearls of Elnhofey or Martial Knowledge, which might be important in highly optimized groups in PvE, but is pretty good in PvP. Disease resistance means no Minor Defile on yourself in PvP which with triple max resource can make you a pretty tanky and adaptable healer.
Life Mender - Increases you healing done by 6%.
Argonian Resistance - Increases you max Health by 1000 and Disease Resistance by 2310. Gain immunity to the disease status effect.
Resourceful - Increases you max Magicka and max Stamina by 1000. When you drink a potion, you restore 3125 Health, Magicka, and Stamina.
Khajiit Acceptable choice for PvE healing, however with weaker bonuses than other races. Crit healing passive might seem appealing, but in reality it does not work that well due to current balance in a game and Critical healing mostly being overhealing (doesn’t matter how hard you overheal), and typical healing builds being non-crit oriented. For the same reason + no defensive passives this race is a not the best choice for PvP, even with triple resource buff.
Robustness - Increases your Health Recovery by 100 and your Stamina and Magicka recovery by 85.
Lunar Blessings - Increase your max Health, Magicka, and Stamina by 915.
Feline Ambush - Increases your Critical Damage and Critical Healing by 12%. Decreases your detection radius in Stealth by 3 meters.
Imperial Normally a tank race, but also a decent choice for PvE and PvP healing, despite not having a max Magicka or Spell/Weapon damage bonus: high max Health and good sustain passive allows easier and safer adjustment with no HP bonus food in PvE. Cost reduction passive works on all abilties, including Ultimate, as a nice bonus.
Tough - Increases your Max Health by 2000.
Imperial Mettle - Increases your Max Stamina by 2000.
Red Diamond - Reduces the cost of all your abilities by 6%.
Nord Another tank race which can be a nice situational choice for PvE healing if you know you’re gonna be constantly taking damage either from surroundings or from Guard skill or for really sturdy PvP healer. More Health and Resistances allows to survive for better and for longer, and you get Ultimate in return. However, in situations without consistent incoming damage it loses to Imperial and Magicka oriented races.
Resist Frost - Increases your Max Health by 1000 and Frost Resistance by 4620.
Stalwart - Increases your Max Stamina by 1500. When you take damage, you gain 5 Ultimate. This effect can occur once every 10 seconds.
Rugged - Increases your Physical and Spell Resistance by 2600.