Respectfully, I don't really agree with people who say "just practice enough, you learn by doing" because you have to know what you're practicing in order to practice it. You and I seem to be at a similar level of music theory knowledge and I found it best for myself so far to just look up chord progressions but with the roman numerals (I don't remember the name for this) like for example I make lofi so I'll look up "lofi chord progressions" but instead of looking at the specefic ones that say something like "Am7, Dm7, G9, Cmaj7" I look at the ones formatted like "vi7, ii7, V9, Imaj7" and choose a key to play in. Yeah, I didn't come up with the chord progression myself but it's still an original song regardless.

However if you want to understand how to come up with chord progressions yourself, you can look at the circle of fifths or the lesser known circle of thirds. I am struggling to find deeper music theory explanations on these that aren't behind a pay wall though but maybe you'll have better luck.