Whens the right time for an API Gateway?

hey folks, I've been working on a few microservice-based projects lately and the topic of API Gateways keeps coming up. I get the general benefits like centralizing auth, rate limiting, and request routing. But for a small system, does an API Gateway just add more trouble than it's worth early on? I'm curious to hear about your experiences and when you decided it was a must-have, not just something to add later when things get big.