Thinking about micro-services as a scaling solution is only ever looked at from the orchestration perspective for some reason. Most of the lessons there can be applied to scale your code as well so that you can spin parts of it off with ease. This also has the benefit of giving you a cleaner & more maintainable code-base so there is still a gain even if you never spin anything off, which could be argued was the problem in the first place.

This is perhaps the best bang for your buck until you actually know what the bottlenecks are as it otherwise becomes a brute-force approach to "scale everything individually". Unfortunately "our code is ready to scale" doesn't quite sound as cool as "we run a thousand micro-services".