You can actually get the doggo very early in the game, even before getting Evil. What you need to do is go to the red slime forest save doggo from the red slimes then sleep at the inn. Go to the forest in the north east corner there's a semi hidden pathway down and you'll find the doggo again and there will be a short cutscene with you interacting with it afterwards go sleep at the inn again. Final step is to go to north west side of the map and find the doggo again and if you have a healing charm 10 I think, you'll heal it and it'll join your party. As a note, while the doggo is in your party in the menu, it can't do battle until Evil is recruited since battle party size is locked to 1 until you sign the contract with her.