I'd be Googling Addressable LED strings.
They consist of LEDs (often red, green and blue together in a single block) mounted on top of a control chip.
Each has a serial data input pin and serial data output pin, with each one taking its own data and passing the rest onwards.
So you only need a couple of GPIOs to feed the first in line, the rest being fed from the previous one.
There are two different systems available, called Neopixel and Dotstar. The latter has a second input and output for a clock signal, meaning timing of the data is less critical, so is probably better.
Many companies will sell you a long string of them ready-mounted in a flexible tube or on a flexible strip.
For example https://www.adafruit.com/product/2435
is 5m long, with 30 LEDs per metre, so 150 LEDs
However, for your project, you may wish to buy them individually.
Again, Adafruit will sell you monochrome ones for $4.95 for a ten-pack, $44.60 for 20 ten-packs https://www.adafruit.com/product/2350
, or save some money and get RGB ones for $4.50 for a ten-pack, $40.50 for 20 ten-packs https://www.adafruit.com/product/2343
Handy break-out pcbs will set you back another $44.60, which might be a good investment https://www.adafruit.com/product/1762
You will have to provide 5v of power to the LEDs. Current-wise, Adafruit is less than helpfull regarding the current required - 200 could to take anything upto or beyond 12A if they're all lit, but just one or two wouldn't need much at all.