I have got the task of coming up with a solution of individually controlling around 250 LEDs. As I would be a complete newcomer in programming an Arduino or whatever else there is, the computing platform is relatively irrelevant for this job (*). It mainly should be portable and not overly large.
The LEDs could be single colour but if there is a simple extension for RGB LEDs, this might be even better. If there is a hard limit in controlling such a number of LEDs and things would be much easier if we reduced this number, we might be able to put three or at most four LEDs on the same controller. (The LEDs will be behind a screen and not directly seen.) In that case, the number might be around 80.
The question is mostly about what would be the best platform choice in this case?
(*): I am mainly a programmer and not an electrical engineer, so diving into a C like library is my least problem. Hardware is my problem.
Edit: The LEDs should be variably positioned. There may be smaller clusters or strings of a few LEDs but otherwise it should be rather arbitrary. There should be ~< 2m between the outmost LEDs.
What's the budget? Do you already have the LEDs?
For that many, I'd probably try to use some "neopixels" (LEDs with WS2812 or similar controller). It can make the wiring much simpler by allowing daisy chain. And you can stick on multiple power supplies if you need based on the number of LEDs and the brightness.
You only need one data pin if they're all in one string