You can deflect arrows and projectiles by swiping at them with the starter blade (not flamethrower though). You can even deflect/destroy bombs from a bomb trap, but not mortar guard bombs I think.
You can use the grapple to find search if a block is a holoblock.
You can grapple in and trigger friendly fire from traps and grapple out in many situations.
You can pass through the corners of acid traps and survive.
Traps and explosions will do friendly fire to enemies so you can use them sometimes to clear out guards.
You can headshot armored enemies with your sword, not sure about the guns but I’d bet that works too. Also pretty sure armored enemies don’t have armor on their backs so thats another way to take them out.
When in building mode you can hold X (if I remember right) to clear everything in the map. I made the mistake of manually cleaning up 2 bases after buying them before I found that out lol.
In your first outpost put down a wall of arrow traps and just practice reflecting them. Do the same with grunts. Also practice hitting the legs of grunts with melee, the armor upgrade only effects the upper body.
Also dont place traps in the area the bolts from the bolt trap land, because the amount of bases that do this is insane.
Also buy the bolt magnet range and bolt vision upgrades for your suit. Now laugh at everyone that tries to steal your bolts.
For base building, try to focus on the largest map sizes (Brutal, 4,500 build points) since from my experience most players seem to quickly graduate towards that difficulty. It also helps you since you get the maximum build capacity.
For your weapons I recommend you unlock some of the alternative weapons so you have options, the Energy Crossbow is great if you run into a map with a lot of mobile enemies as an example, and can make a good replacement for your sword.
I also suggest upgrading your main gun at least once as this gives it an extra shot. Its not much but the third bolt makes a huge difference.