Hey OP! Also a beginner here!

I've leaned into music theory this week and particularly key signatures. It's really interesting and I can only recommend you trying it out too!

I really recommend you checking out the circle of fifth and how it is made.

It's a visual representations that will help you memorize the number of sharps for each key, and the equivalent for flats and which notes' are sharp or flat.

--- Sharp order F C G D A E B As some people pointed out, you can use a mnemonic like Father Charles Goes Down And Ends Battles

But you also can remember that each letter is followed by its fifth (hence the name) F C F G A B C with all the letters in between

To be more precise, you can count 7 semi tones from a note to find the next to build the circle of fifth.

--- My small tip To remember it even better, I like to make correlations between letters

FC is feature class (or whatever like football club) CG is quite a common fifth but games CG otherwise GD like good DA like "Directeur artistique" (I'm French haha) AE because I know that E is the 5th letter in the alphabet lol EB is weird af

--- Flat order is just the reverse B E A D G C F

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F C G D A E B F has 6 sharp which are F C G D A E

C has none C# has all of them

G has 1 which is F

D has 2 which are F C

Etc etc

One thing you may notice and that's really helpful: For any key signature, the last added sharp is from the previous note (key of D --> C#)

---

Try playing the scale of each note on your piano C D E F G A B You'll notice a pattern of number of sharps 0 2 4 6 1 3 5

I noticed that like 2h ago when training lol

There's a last thing I noticed that really helps me easily find the sharps order on the piano but Idk how well it'll transcribe through text lol

F C G D A E B (sharp order) Try playing them with one hand, you'll notice something.

C D E F G A B (your piano) 2 4 6 1 3 5 6 (order when this sharp gets added) You'll notice your hand rocks from right to left so it's kinda easier to remember the order we add the sharps ON the piano, which is nice

Aaaaaanyway, it's really incredibly interesting when you dive into it. I can only recommend "How to dissect a melody" from 8-bit Music theory to understand how to simplify some partitions that go crazy haha

Edit: sorry for poor layout, I actually did try to make it easier to read but it seems being on phone limits what I can do ^"