To do the most damage, you don’t want to use Avalanche at all, as it lacks significant multipliers to do decent damage. Instead, you want to get all your damage from Earthquake, which means wearing the Girdle of Giants belt.
For more info, you can look at the Maxroll guide that DM linked, or consult my own guide on the build, which is the most in-depth source available: [Guide] MOTE6 Earthquake