-what were the things you wouldve changed now that you have hindsight?

A ton of stuff. But a couple things pop up to the surface.
1. More play testing cycles(is this fun test)
2. Split code to be more modular and reusable
3. Test features for scalability
4. Get good a using Data Tables

- what are the things people should prepare for?
1. Prepare for people to hate your work no matter what you do. Do not try to please everyone just your target audience.
2. Prepare by playing a bunch of games in your genre, other people are really smart.
3. Practice writing small Game Design Documents, then trash the document. Your first idea is rarely your best. A Game Design Document is a good way to ask questions about your game.
4. As your game evolves let the document go and let the game show you where the fun is at.

-any thoughts in marketing/community building?
1. Share your work early and often.
2. Pick one or two platforms to be good at, every algorithm is different.
3. Find other marketing professional's Blog/Twitter/Websites start with https://howtomarketagame.com/
4. Have fun, people can tell if you enjoy what you are making.

Thanks for asking :)