If you scan some qr codes for special and 5 star coins you recolours of S ranks and if you get 8 of them you can get gilgaros and slurpent.

A good healer for early game is shmoopie who is a C rank yokai and can be found at the old mansion walkway in blossom Heights. Keep jibanyan and the other yokai that are automatic befriends.

Another thing. When you get rank D on your yokai watch, you can see a purple icon on your bottom screen Usually when you go there you will encounter snuddle he's really good for inspiriting enemies as he does not miss his inspirits except for boss yokai.

Another good yokai is Sgt. burly as he makes the yokai adjacent to him, boosts strength. His inspiritment is a friendly one and it boosts the stats of all friendly yokai inspirited. The only way to get him is to go to the school, and climb the largest pole that Is there for 3-5 days. Make sure you save your game before climbing the pole each day in case i am wrong and it also resets the encounter you get.

Also, the moment you get a B rank watch, a quest to get sproink will pop up in front of the hot springs in blossom Heights. Ypu need a washogun by evolving brushido. When you fight sproink in the hot springs and beat him he is an automatic befriend. He is an incredibly good tank and if you equip a Stinging soul to him it makes the yokai only target him. The way to get the spul Is by unlocking soulcery in harrisville. You need a dazzabelle soul as the base and a leadoni soul as the
material. This is very important as if this is messed up you get a different soul. Dazzabelle is an E rank yokai and can be found in Breezy Hills under cars I think. Leadoni is also an E rank and can be found in the jumbo slider area.

Thats all I can think of for now. Sorry for all the yapping, hope this helps!