What do you mean by best stat? Like stat spread?
That'd be 1634 for a mage and 1643 for anything else; since secret empathy points are random is best if the stat that determines the guardian is 2 points higher than any other
As for skills, the less the better, that way it uses them more frequently
the skills I would take are Skunk Pouch and if you have myshop either Shard of Glacier if you're an electric mage or Shield Breaker if you are a non- mage
Also check Almora's guide
for general info about guardians