Want 500 insignias

I am a dojo 8 player with a max level fireguard of level 9. Rest all are below 9. Ranging from 5-9. I currently have 7500 insignias, and I need 500 more to purchase a skin.

But, here's the catch. All my characters rank is either 15 or above. And I am finding it very tough to reach rank 20. My highest trophy is with itu, which is level 7 with 2 abilities unlocked(470 currently). So, I think I will have to grind and leave my luck on nekki(as my opponent is always at least 2 dojos higher than me).

What should I do to earn 500 insignias? Plz suggest some alternatives.

Can I earn insignias through 3v3? I have 1700 trophies in 3v3. So, there also I'm getting high dojo players.