Use the Murderous Intent talent if you're planning to main heal. Cursed Accord's healing increase but damage reduction is too great for it to be viable late game.

Blood Cannon
Armor
Increase extra Blood Health by 1250 while decreasing base Health by {scale=125|125}.
Level 5

Wings of Terror
Death Wings
Increase the lateral movement of Death Wings by 18%.
Level 3
Blood Canon 4 - 5 is mandatory for any Lilith build.
Wings of Terror 2 - 4 gives Lilith incredible mobility and makes her harder to hit when using her movement ability.

Sheer Ascent
Death Wings
Increase vertical movement of Death Wings by 5%.
Level 1

Sanguine Pact
Death Wings
Reduce the Cooldown of Blood Hex by 1s after activating Death Wings.
Level 2

Unholy Flight
Death Wings
Reduce your damage taken by 20% for 1.5s after activating Death Wings.
Level 4

Waning Moon
Blood Hex
Reduce the Blood cost of Swarm by 20% while an ally is marked by Blood Hex.
Level 4
Sheer Ascent 1 - 2 helps you get to high ground more easily.
Sanguine Pact 2 helps make your Blood Hex more readily available.
Unholy Flight 1 is amazing value for a level 1 card.
Waning Moon 1 - 5 makes your Swarm cheaper, no downsides.

Enriched Blood
Swarm
Increase the damage and Healing of Swarm by 20%, but reduce its duration by {scale=0.35|0.35}s.
Level 5

Convenient Leech
Swarm
Reduce the effect of Crowd Control for allies within Swarm by 25%.
Level 5

Symbiotic Relationship
Swarm
Increase the Healing allies receive from Swarm by 20%, but increase its cost by {scale=4|4}%.
Level 5
Enriched Blood is a DPS and healing output loss.
Convenient Leech is not a terrible card but most teammates would rather build Resilience since it's more reliable anti CC.
Symbiotic Relationship's cost increase for the healing increase is nice in theory but in practice, not consistent enough to warrant the extra resources you'd have to use.

Morale Boost
Armor
Increase your Ultimate charge rate by 30%.
Level 3

Kill to Heal
Armor
Getting a kill or elimination heals you for 600 Health, unaffected by Anti-Healing.
Level 3

Haven
Armor
Reduce the Damage you take from Direct and Area of Effect attacks by 6%.
Level 1
Morale Boost is there to boost your survivability. Your ultimate is better to be used as a health regen button rather than used to buff your allies. Use your ultimate when you are around 50% health, don't let your health get too low unless you can hide to recover.
Kill to Heal gives you more resources to heal and add that to the blood HP you're naturally getting back after a kill, you can come out of a team fight with full health.
Haven over Veteran because Veteran doesn't affect blood HP. Haven would give you more value.
Use Maelstrom of Carnage if you're playing as a off-healer or if you're team is dive heavy. While this is Lilith's damage talent, if you can play Lilith at a high level then you can main heal with this talent. The healing playstyle is much more aggressive and mobile. Use your Death Wings often to jump between allies and dive alongside them but you also have to maintain your blood HP since you're going to combo Death Wings with Swarm a lot. The difficulty of the playstyle comes from making sure you have enough blood HP to go in, maintain Swarm upkeep, position yourself so that your Swarm touches both allies and enemies while keeping track of Blood Hex to regain blood HP so you can survive while still keeping Swarm up.

Blood Cannon
Armor
Increase extra Blood Health by 1250 while decreasing base Health by {scale=125|125}.
Level 5

Wings of Terror
Death Wings
Increase the lateral movement of Death Wings by 18%.
Level 3
Wings of Terror 3 and Blood Canon 4 are important cards. Play around with Wings of Terror and Sheer Ascent to determine what works for you.