Greenish Moon

About as simple and straightforward as you can get: make a ton of money, and use it to build huge walls with Sandburg.

Anson Rose and Dedication Ceremony helps speed up the process, and even gets you a janky alt win condition with the threat of a lethal Woodcutter facecheck.

While runners are definitely just a bit too rich these days, the persistent income sources backed by Encryption Protocol and Gagarin Deep Space: Expanding the Horizon's passive ability is pretty painful even to the well-off. Punching through the Gagarin Money Fortress is decidedly not budget-friendly.