I’m not going to go into details on how I did it, since some of it cost money and time I didn’t necessarily have at the time. But I’ll let you know my current personal rule:
For serious use guns I’ll only change something out/upgrade it when I can identify a specific problem that can be addressed by a specific change of gear without affecting the reliability or safety of said firearm.
I sucked at shooting today, at the match etc. isn’t a specific problem. That’s a general problem, and the first question I’ll ask myself is “have I been practicing enough to perform at the level I expected to perform at?” The answer is usually no, so I’m not allowed to change anything.
Some examples of things I have changed and why.
X front sight is wider than a B8 at 25 yards, and has no light bars on either side of the rear sight. I know through experience that a thinner front sight with some light on either side is more precise for me so I got some thinner sights with a wider read notch.
This gen3 glock is all slippery and it negatively effects my ability to maintain a good grip during a string of fire. Ok, time to add some grip texture.
Being able to try out something new on a friend’s gun or a friend’s different gun can sometimes be helpful, but can also yield a false positive because sometimes you’ll concentrate more or differently when trying something new.
I’ll also third or fourth the message that dryfire with a red dot was an extremely useful tool in improving my glock shooting.
In regards to @okie john’s post above, I once put in a much worse than my normal performance at a local class/skills day. I took the last box of ammo from that day to the range a week later and it wouldn’t hold a 10” group at 25 yards. A quick group with some +p gold dots had me feeling better about my previous and then current performance level.
You’ve already gotten better advice than mine here, so good luck with your journey.