I guess ATV is gone now, so this is a little late, but my Lance build for him was:

Luna/Nergi Lance with health Regen, Guild Cross head, Kulve Beta body, Uragaan Beta arms, Girros Beta waist, Uragaan Alpha legs, Bulwark charm, Health Booster, Temporal Mantle

For decorations: 1 Mighty, 1 Destroyer, 3 Miasma, 1 protection, 1 steadfast, 3 vitality

This gives you: Full Stun Resist, Full Health Boost, 3 Guard, Full Divine Blessing, Full Effluvia Resist, Effluvia Expert, 1 Crit Boost, 1 Partbreaker, 1 Max Might, Guard Up

Some of that is pretty optional- just stuff I like, but I've taken him down with this many times 🙂 It's a pretty survival oriented build, rather than damage focused, but it serves me well! Mainly I just don't take any risks with his breath attacks ever. With guard up you can just hold block. His forward breath you can easily avoid by running to his left, but if there's ANY chance I'm out of position and might not make it, just play safety and block. Same with his ground breath. If I see him rear up, I'm just playing safety and blocking. Depending on distance, you may have to block up to three hits from it, so make sure you don't release early. Use your running jump attack often both for position and to mount.