Energy as a resource gates play differently than mana. Mana-gating rewards accuracy and harass, Energy-gating rewards proper comboing.
For example, mana champs have a large pool with a large number of possible spell casts at their disposal. Miss too much though, and you mana starts restricting after a while.
Energy champs, however, have a much smaller max pool before they start getting restricted, but it comes back very fast, which means a lot of damage in a small amount of time is the way to go with energy champs.
Try getting the combos down, and then be patient between combos. Going in without enough energy at the start will restrict in the middle of a combo and cause issues. Also, energy runes are just not worth it. It's not worth the hyper specialized rune page and other stats are far better for your game.