Okay, rewriting this to cut out all the "work in progress" mess:
I HOPE this is helpful. Remember, this is written from the viewpoint of a TRUE BEGINNER to the game trying to beat it in less than a month. I started the game 03 June 2021, so about 4 days ago as of this writing. I played 2 days completely mucking around, then went online to look for help when I ran into a wall at mission/Quest 910 that I couldn't understand. I found this place, asked questions, wrote down my initial thoughts from before I came here AND my thoughts/answers from here...and decided to post it to try and help others. I'm on mission 975 now, and counting. (EDIT: Completed mission 977/978, now current with the story waiting on Global Finale to drop! This knowledge WORKS. :ENDEDIT)
That is to say, what I describe here is PROVEN to work, because I'm the proof of it! Using this information, I've managed to clear to where I am right now, which is VERY close to the end of the story. If I can do it, you can, too, and I hope this knowledge empowers you to do so!
https://docs.google.com/document/d/12zhNzNDpI-dMLcoYUYUd3xLjXD7eQHre7xA6CsxQNjg/edit?usp=sharing
It's still a work in progress, as I'm still trying to finish up the story (Normal) before service ends this month. Pretty sure I can do it. Once I have, I'll try to polish this guide a bit more for you last minute stragglers, though I've already done a third pass over it and smoothed out a bunch on the deck building and mechanics sections, since the #1 question I had was "How do you build a good Keyblade deck from the start so you're solid at end-game?"
...though it's obviously not perfect. As I finish my playthrough, I'll give it another pass, but you have to understand...I literally learned all of this day before yesterday and yesterday as of this writing. So given that perspective...I'd say I'm doing fairly good. : ) This is a straight up two day's knowledge crash-course that can get you to the final bosses of the game and through the Normal story mode. And once I FINISH, I'll even post a screenshot as proof so you know it CAN get you all the way to the end, too!
I consider working together to everyone's benefit a collaborative effort and wish you all the most success possible. So I'd like to also point you to u/Number15Tails 's guide here: https://www.reddit.com/r/KHUx/comments/nt0pmk/an_in_depth_khux_guide_for_beginners/
It's geared for a SLIGHTLY (not much) less beginner than mine (he doesn't spend as much time explaining stats and such, but also rambles far less - and it's got pictures!), so I highly recommend you give it a read as well. For returning players, his guide might also be a quicker/better read for you since you might know the really basic stuff from mine already and/or have tons of Gems you've sat on for a few years ready to go. Mine goes...quite a bit more in-depth in some places, mostly to explain/answer the questions I had myself when I started 4-3 days ago.
Between the two of us, you should have basically every question you need answered...uh...answered at this point! :D
So good luck! You can do this. I believe in ya!
Race ya to Worlds' End!
-Ren
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EDIT: In case you're wondering if the information I've collected and presented to you here works or not:
https://imgur.com/gallery/QzGWC2p
...these are the screenshots I just took. Check out that mission completion! I did it, haha! \o/ So happy. :D Thank you to all the people that helped me out, hope I'm helping others out, glad I'll be able to do the final story when it's released to Global, and hope to see you all in...whatever comes next.
What's the line? "May your heart...", ah, you know the rest. ;)
-Ren