If legendary could only bring 3 toho kaiju, who would it be?

Anguirus: A skeleton resembling him briefly appeared in King of the Monsters, so they could easily introduce him, with the skeleton being another member of his species. Or, as DangerVille suggested, the skeleton could actually belong to Anguirus himself, with the series introducing him in a story set in the past that eventually shows how he died.

Gigan: They've already established the idea of aliens in the MonsterVerse, so they could do a classic alien invasion storyline, with Gigan being part of their army. Plus Gigan is just so bizarre, it would be a missed opportunity not to include him.

Destoroyah: The Oxygen Destroyer has already been introduced and used in the series (and it could possibly be used again), so Destoroyah seems like a good candidate. They could introduce him (and possibly an army of Destoroyahs) in the last MonsterVerse film, being a massive world ending threat that Godzilla, Kong, humanity and the other Titans have to face off against in one last battle to protect the Earth.

None, going forward the mv should focus on being more original instead of nostalgia banking with toho monsters.

Using toho monsters is toho´s job

or focus on using the Toho monsters already in the Monsterverse. I felt like Rodan and Mothra could have been focused on more in King of the Monsters but they're significance was drowned out by the OC kaiju

Daigoro, Goliath and Maguma.

I recognize Maguma but not the other two

I'm bad at making decisions :]

Anguirus, Gigan, Destoroyah. though if youd said 5 id add in Kumonga and maybe Varan though Baragon would tie for that slot

Orga - Huge potential with his DNA stealing ability, could be a good final villain. 

Hedorah - Banno got us this universe, his creation should get the spotlight he always wanted again. 

Destoroyah- "set up". Would be cool to witness again and really hurt Godzilla if not kill him.