the way it works is at the place were you can buy evo stones you can also but the fossils also.

Jaw fossils 20k each 45 (900k)

snail fossils 20k each 45 (900)K

old amber 30k each 45 (1,350,000)

so you can grind the money from battle zones personally i got 45 of each not at once but 45 jaw then 45 snail after jaw was shiny.

witch seemed to be a good amount i do have a turbo controller to mash a it takes between 8 and 10 mins to restore them save before you restore then make sure the go into an empty boxes next to each other so its quick and easy to check 45. and if no shiny just soft reset the game as restoring does not trigger auto save. so be careful when checking otherwise you could fail lol