What Character Should I Main to Learn SSBM?

Hi everyone! I'm a brand-new SSBM player looking to take the game more seriously, and I want to commit to maining a single character to focus on improving. I've tried every character on the roster, but I'm super indecisive and can't settle on one. My goal is to pick a character that teaches me the fundamentals while still being fun to play. Right now, I'm considering the following:

• Fox: I love how smooth Fox feels to play, but I know he's extremely technical and can take a while to see real results. Also, I feel like I am fighting myself more than the other person a lot of the time. That said, his movement is so satisfying!
• Luigi: I love his silly personality and joyously slippery wavedashing, but I struggle with his air mobility and feel completely lost in some matchups. Plus, there aren't as many guides for him online.
• Donkey Kong: DK is so fun, and I adore watching Junebug’s gameplay, but some matchups feel like I can't even play the game, and DK also seems to lack online resources.

What do you think would be the best character to learn the game with? I’d really appreciate your advice and any tips you have for a new player! Thanks in advance!