Serious advice I’d give a friend I care about…
You seem to have serious “part envy” which is what gets us in trouble in a game like this. We see these cool parts in the game that we don’t have and can’t acquire easily, so we get frustrated and demoralized.
Don’t let that happen to you.
You can do very well in pretty much every game mode with very few parts, but you have to be strategic in what parts you get.
For the rotating daily challenges, you’ll need a cannon build, a shotgun build, and a machine gun build. Supporting parts for shotguns & machine guns are pretty much the same (radiators, coolers, cabs etc).
Canons will need their own set of supporting parts (ammo boxes, flywheel, cabs etc).
So, focus on getting a good machine gun or shotgun build first.
I’d suggest Sledghammers and/or vectors and if you like them, upgrade to Maces and/or Sinus-Os. If you like THOSE, fuse em. (don’t get rid of the sledges & vectors, though)
Are there more powerful shotguns & machine guns? Yes, but they take one more energy. In some ways, the Sinus-O and Mace are “end game” weapons in that you can go higher rarity, but PS-wise, you’re not really getting that much better of a weapon - if at all.
Another reason to go this route is these are core weapons. They’ll always be viable through the nerf/buff cycle.
Take the advice for what you will… this is where I am, and I still have sledghammer, maces & Sinus-O builds saved in my blueprints for use when those challenges come around. Meaning, I have much higher rarity weapons , but I choose these “lesser” weapons for good reason.

I chased those cool looking weapons I didn’t have for a very long time, and that’s one of the biggest regrets I have in the game. I wish I’d stuck with some basic weapons, got good with them, fused those builds completely, and then… and ONLY THEN… gone after the cool stuff.
At the end of the day, I rarely use my parsers, avalanche, heather, reaper, waltz, destructor, vindicator etc etc etc… They’re cool. They’re fun… but if I want to win and do well dependably, I go with the basics.
Cannons are another issue. I hate all of 'em and use Assemblers. I wouldn’t suggest that for most folks, though. They’re a handful.