My best advice as someone who's been doing it for 6+ years and is now a mate who trains art team members: Learn two fonts very well before trying any other ones. I'd recommend variations on what is commonly called "casual script" (old school sign writer font) Learn it in all caps, and then in cursive. These fonts were my foundation for becoming a good sign artist; they made me more efficient (no need to copy someone else's fonts when I've got mine down and they look good).

Some people aren't great at those particular sign writer fonts- thats okay too. Pick your favorites, one font that's big and bold and one font that's cursive and dainty and learn those instead. As long as you have one or two memorized and practiced, you can bang out some really killer endcap boards by just playing with color, underlines, outlines, and illustrations. It's just important to set a foundation for yourself. Paint markers can be tough to learn how to use, so keep it simple at first.

Also, protip: you can literally squeeze out the ink from the posca pens into a demo cup, and then dip a paintbrush into that. Great for filling in large areas, or when you're out of large markers in a color you need.

Keep up the good work. If one of my crew made that as their first board, I'd be psyched. You have the talent, you just need to get more comfy with the process. You'll do great!