Which lane are you playing in? If you can shove mid fast enough, it's not a big deal to shove it into the opponent's tower and back off until the next wave comes. Make sure to buy wards every time you back. Same thing top, except because most top laners are melee, you can usually get away with farming without your e, not to mention because you can ward river easily, pushing up isn't a big deal either.
If you know you're going to use lots of mana to harass, then start with flask. I usually don't harass unless I can heavily chunk them out (pretty often actually if they overextend a bit trying to poke me or to farm), land your q and you can get lots of free autos off. Remember to move between attacks. If you really need some guidance, go look on youtube. Wingsofdeath for top, and bjerg for mid. You only have to watch the first 10 or so minutes since you only want the early game.
While your hybrid build is fine, esp if it's working for you, I feel like hybrid kayle actually falls off harder late late game compared to full AP kayle, so my preference is to go lich bane, void staff, possibly dfg instead of triforce, guinsoos, and gunblade. But as I said, if it works for you, it's fine. And hybrid kayle is a monster mid game / early late game.