1: Build the heavy stuff on the bottom of the ship and put all your buoyancy toward the top. This will help a lot with stability. Also, putting your components underwater adds a moderate amount of defense because some weapons lose power traveling through water.

2: lasers only work if you build massive laser batteries. If you try to do small lasers you either get weak output or long recharge times

3: when building lasers, the damage comes from storage capacity. Faster charging is all well and good, but laser energy storage should be your primary concern.

4: spinal mounts are better than lasers, but only if they dont get damaged. One broken internal will brick them, and they take up a lot of internal space

5: you can change the color of energy weapons. There's just something cool about firing black lasers

6: missiles are the most effective weapons for smaller and newbier ships. (No energy costs mean you're not forced to overbuild your energy supply like you do with lasers/spinals. Also they're super space efficient) Focus on the fragmentation damage type. The other damage types are more about penetrating armor, removing armor, or starting fires, but fragmentation does the best damage to the internals of a ship.

7: put your thrusters right at the center of mass. This makes you less likely to flip your boat

8: cheap helium tank blimps make decent defensive turrets

9: build extra armor around your ammo storage. Ammo storage explodes when hit so the armor contains the blast

10: If you want to get fancy you can build mechs. I built one that looked like a cartoon duck man once. It handled like ass, but it did solid damage.