With the press of a button, I need to play an intro sound file, then one of 50 other sounds in order, each time a button is pressed
You will find all the code and thelibrary you need on the Adafruit learn center.
For such a project I would use a DF-robot (clone) MP3 player (~4$), an Uno, a speaker and an SD card. The library for the player includes examples to get you started and the sound project you plan is possible even with low programming skills. Look at the example codes provided and start to program.