Barrel roll as much as you can to avoid taking damage.
Your ship's secondary attack delivers a much-bigger punch than standard fire. To use it, tap the intended target and watch that sucker explode.
You'll earn Arcbucks by destroying bad guys and collecting cubes that appear on-screen. Try and get most of is you'll need it for upgrades.
Visit the Hangar and spend Arcbucks you've earned during earlier missions to upgrade that spacecraft, purchase a new one and pick up more powerful weapons.
Wormholes are bonus missions that challenge you to complete a specific task, like gathering all cubes/shooting targets without missing a single one, or navigating through a tricky environment. They're a great way to add more Arcbucks to your pocket.