There are food items that can grant Battle Exp. You just have to have them on hand, or find a way to find them, or buy them- at least for levels one and two. When leveling/Digivolving happens, then you get to re-roll your HP and Energy modifier (die times level) and apply the new Vitality and Wisdom bonuses respectively. Hit-points and Energy do not increase as Vitality and Wisdom are invested.

Also, I see you there, [@BrokenVeil]. Why don't you say hi?