@Rainydeity I'm so happy to hear that you're enjoying KB!! I'm also flattered you thought to ask me!! I can offer some advice that I did when I made Jug if it may help!
I think having a theme is a great start. JJBA stands are all based around themes, which makes it easier to make an oc because it sort of creates a template. Like how Stardust Crusaders are all tarot cards and DIU are all music themed, you just kind of go along with that!
What I did with Jug was think about what kind of character I wanted MC to be and find a band with the vibe that represents that. Another thing to keep in mind is that stands are a reflection of the user's soul, so if you have a bright, happy character, the stand will also be bright and cheery. Or if you have a character who puts on a mask around other people, their stand will reflect more of who they actually are, like with Jotaro and Star. Jotaro tries to be all nonchalant and edgy, but Star is curious and expressive.
Also, JJBA is a crackfest, so if you have an idea for a really extravagant or op stand, it'll fit in well. I'd say the hardest part is figuring out the technicalities. Like range, power, and stuff. That all is up to interpretation! The best part about JJBA is that it doesn't necessarily have to make too much sense.
I hope this helped a little! If any if this doesn't make sense lmk and I'll do my best to clarify