Over the past few weeks, I worked on building my first reusable SaaS starter kit using Next.js, Prisma, JWT authentication, and Lemon Squeezy billing. The goal was simple: Stop rebuilding the same foundation every time I start a new SaaS idea. But while building it, I made a lot of mistakes — and honestly, those mistakes taught me more than the successful parts. Here are some of the biggest lessons I learned. 1. I Tried to Build Everything at Once At the beginning, I wanted the starter kit to include: authentication billing teams admin dashboard analytics notifications multi-tenancy Basically… everything. That was a mistake. I realized very quickly that trying to build every possible feature slowed me down massively. The turning point was when I focused only on the essentials: auth dashboard billing clean architecture Everything became simpler after that. Lesson: A smaller finished product is better than a huge unfinished one. 2.…