Using this, we would calculate (using just @WSG examples) that if we were to want each to deal 60, then we would do 60/(Default Damage for Gadget) and that’s what you multiply it by. For the quantum portal, you would x by ~1.3 and so on. Use this formula for each of them. Twister: ~1.9.
Full List
For gray rarity:
:Pickaxe: x 60
Wand: x 3
Zapper: ~4.8
Stone thing: ~3.3
Evil Eye: ~ . 83
Muffin Launcher: ~1.36
Snow Ball: ~2.14
Sling Shot : Does exactly 60 damage
Blaster: 3
Gadgets: An Overview, Ranking & Practical Uses
Used this guide 
Hope that helps! Just find the ratio to times it for more damage! (Example: to get 120, times the amount that you times each one by 2)
I might’ve done smth wrong, so let me know.
(I’m also not 100% sure how the multiplier works so yeah…)