Learn how to code and learn the basics of (FastLED) first. There's lots of examples online.
Break it down into individual components (i.e. buttons, IR, LED's, Bluetooth, serial communications, demo sequences).
Create test 'jigs' and programs for each component.
Slowly combine the functionality and make sure you incorporate lots of testing.
Learn to use git for version control.
Be prepared to throw it all out and start from scratch with your newly acquired knowledge.
Oh, and if you're using delay(), be prepared for your button polling or other input routines to be unreliable.
Learn how NOT to use delay() statements.
Comments are a thing. Use them.
Keep your loop simple. Put stuff in functions.