Lifegain Commander (EDH / Commander)

Bring your Commander in turn 3.

For you most likely being over 30 life total at that point, It flips and is a Legendary Enchantment, that prevents all forms of damage to your creatures.
Therefore they are nearly indestructible, except through 'destroy' or 'exile' effects, like most Board Wipes or Single Target Removal Spells. But against creatures you now have an almost indestructible defense line, when yours are not tapped.
These might help best: Wall of Glare, Guardian of the Gateless, Brave the Sands, Goldenglow Moth.

Play lifegaining instances. . .

. . . like Soul Warden, Fountain of Renewal, and Impassioned Orator to trigger your things.
Your things are Ajani's Pridemate, Gideon's Company, Crested Sunmare, Griffin Aerie, Attended Healer, Heliod, Sun Crowned and such stuff.

Your things for card draw are Dawn of Hope, Cosmos Elixir, Well of Lost Dreams + some non-life-triggered card draw like Mind's Eye and Alhammarret's Archive, which is also a buff to your lifegain like Rhox Faithmender and Angel of Vitality.

Get your things back. . .

. . . with Emeria, the Sky Ruin, Sun Titan, Brought Back, Cosmic Intervention and Faith's Reward.

Win. . .

. . . through combat damage by getting a lot of Tokens through Griffin Aerie, Crested Sunmare, God-Eternal Oketra, Attended Healer and Resplendent Angel.
Alternatively win by decimating enemies with Angel of Destiny or 1-turn-delayed with Felidar Sovereign or instantly with Aetherflux Reservoir.
These might help best: Celestial Mantle, Beacon of Immortality.

Going more budget friendly:

Cut Archangel of Tithes, Archangel of Thune, Elspeth Tirel, Teferi's Protection, Smothering Tithe and replace with anything (e.g. from Side- or Maybeboard or with an additional basic land)
Replace Land Tax with Plains.
Replace Nykthos, Shrine to Nyx with Plains.
Maybe cut Resplendent Angel, but keep Heliod, Sun-Crowned ;)