Tracks and body breaks give you investigations.
Just fight him in optional hunts and hope to RNG that you will get his investigation.

In Deviljho's case it is important to specify which one you're referring to as normal Deviljho is high rank exclusive and cannot appear in GL. Do some high rank research quests, elder dragons specifically and it's bound to appear at one point. Savage Deviljho appears in any GL region level 5 and tempered one at 6 and 7, so keep grinding there or maybe meld some lures if possible.

Originally posted by jestemjen:

i have almost all gold crowns but i need devilho. the guiding lands is great but it seems like deviljho is the only monster you can't get there? but when i try the safari or picking up tracks in expeditions and quests in all areas, it is never deviljho. does anyone know a good way to get at least some deviljho investigations?

Deviljho is HR only; not really in MR. MR is more Savage Jho's turf.
Go check your HR investigations and bounties at the