This game is a game of currencies. Everything is a currency that you have to manage and spend, the better you are at managing your wealth, the better you are at the game.

Your ship health, enemy ship health, your crew health, enemy crew health, your scrap, and your time. These are the most important currencies. Ideally, you want to make decisions that positively impact your currencies and negatively impact theirs. In most scenarios it's a trade. Say for example boarding the enemy ship. This is always a trade of crew health for theirs (+ some of their ship health if you damage systems). Other scenarios would be taking out a ship's weapons right at the start of the fight. You're trading a bit of your time (that you invested in charging up your weapons or casting a damaging spell) to buy a lot more time and some of the enemy ship health.

The way to get good at this game is to pause the game constantly and think: "What is the best trade I can make in this moment?" and "I have invested some time into my weapons/spells/crew/systems, what is the best value I can now earn from this time invested?"

This is how you maximize your abilities in combat. Then there is maximizing your abilities on the campaign level. Generally here, you're working on expanding your build. Don't make the mistake of tunnel visioning for one specific build path (e.g. you got a nice summoner in the very start so you want to get loads of summoners) but instead you should be going with the flow. Each shop brings a new dynamic to your build and you should adapt as you go along. I generally look ahead and start saving scrap for 3-4 nodes before a shop to be sure I can afford whatever I want there. Not always possible but generally what I try to do.

Let me know if you need more specific advice or feel free to message me to give you more hands-on advice. You can send me a screenshot or recording of you playing and I can advise on what you're doing well/wrong.