The first thing to spend your experience on is the Alien Knowledge perk. It permanently increases the amount of experience points you earn. Grab the first level as soon as possible, and always prioritize upgrading it when you can.
Unlock new moves before upgrading other things. In particular, grab the double-jump as soon as possible. These increase your options for navigating each area’s obstacles.
Don’t waste experience points on unlocking the story missions. You can get those on your own, so those points are better spent elsewhere.
Some enemies require you to slide and attack at the same time to hurt them. Any alien that looks like it’s reaching out to give you a squeeze probably requires you to use this technique.
All of the bosses have a trick to them. For example, the boss of the second stage will swipe at you with two of its tentacles. One is armored, the other is not. Guess which one you need to swing your plasma sword at?
Generally speaking, it’s safer to stay on the higher paths. Just be careful when switching to a lower path as you can’t see where the pits are from higher paths.
Make full use of your moves. Once you’ve unlocked the double-jump, downward stab, and air-charge, you have a lot of control over your mobility. The downward stab will take you directly down, which is useful even when enemies aren’t under you. The double-jump can pull you out of a pit if you’re quick, and the air-charge is useful for crossing gaps.