Overwhelmed on Quests

Event quest lines should always come first.

I would work on the monorail next as you can create donuts when completed. :)

Ignore KL for now as I hear it's bugged. :/

I would do the event quests first since those will go away, never to return, once the event is over. The others will still be there waiting for you later. But it can be a tough choice since some of the other quests will allow you to level up and get more characters that help with the event.

I'll be the odd one out and say do Level quests first since you need many of those characters to do events and Rail yard and Heights and everything else. Depending on your level you may not be able to finish events on time (don't worry, there will be more events)
Rail yard is cool... but it can wait, it's not going anywhere. In my 2nd town, level 939, I haven't started it yet
https://i.imgur.com/kKwq4hy.png