But by turn 280, I was rocking 1200 culture per turn and more tourism than Kongo
Note that what matters in a Cultural Victory is Tourism, not Culture. And I forgot to mention Rock Bands: use them, and exclude them from your territory. Get Open Borders and a Trade Route with anyone with less Tourism pressure than you. Also, the Golden Age dedication Wish You Were Here.
I love seeing what other people say about strategy, because in some ways I play the exact opposite!
Anyways, one way to learn how to win is to play some games at a very high level of difficulty (compared to what you're used to). Get overwhelmed by the AI. Observe what it does well, and try copying that. Observe was it does poorly, and try exploiting that.