I am looking to start leveling a Jedi Knight Sentinel. Is there a certain order I should be using abilities or just use whatever is available? I can never seem to be able to use still without having lots cooldowns to wait on.

Leveling anything can be tedious and seem like you never have buttons to push. When all your "major" abilities are on cooldown, really all you can do is fall back onto the focus-neutral rotation of Strike -> Slash. That way, you'll always have focus for the more potent abilities when they come off CD and you always have something to push, even if it's rather bland. Things will get better as you gain new abilities, though, so you just have to press on.