Horses are a great companions in The Legend Of Zelda Breath Of The Wild, each with thier own stats. But if you want an easy to get horse with great stats being 4 out of 5 in all three catagories, then Epona is the horse for you.
Epona can only be summoned beyond time and space by using the Link Amiibo (others might work but I've only gotten her with the Link one). It's a rare spawn so it might take a few tries to get her. I here that if you reset the game after using an Amiibo withoout saving will let you have another try at using the Amiibo.
After getting Epona I suggest bringing her to the stables to get her registered so you can summon her from any of the stables without having to use the Amiibo again. Unlike other horses you cannot give Epona a new name, but then who would want to give the legendary horse a new one.