I can’t offer much help on reading material on applying scales to your daily routine or songs beyond this: mastering scales so they become muscle memory allows you to call upon them without much thought if you find yourself improvising, composing, etc.
For me, they also help hone my aural skills. Being able to audiate, or hear the music accurately in your mind before it is manifested in your playing or singing, is a crucial skill to develop, and playing different scales, keys and modes helps my ear to memorize the sounds of certain intervals. Then, when I look at new music I’ve never heard before, I can more or less accurately “hear” the song in my head without ever touching an instrument.
That takes a lot of dedicated practice, and I haven’t been that rigorous in many years, but it worked for me when I was developing as a musician. As I’ve paraphrased before, my idol Rafael Méndez once said the key to gaining virtuosity on an instrument is to “play scales, scales, and then...more scales.” It may not be fun or interesting to some, but it really can do wonders for your basic proficiency, even if you only devote 5-10 each day to it in your routine.
I picked up a copy of “The Ultimate Ukulele Scale Chart” by Hal-Leonard for a couple bucks from my local music store when I got started, and I use it almost every day when I practice. Having the visual reinforcement for the scale patterns, even though they stay the same as you move up or down the fretboard, is really helpful for a visual learner like myself.
Hope some of that was helpful! :shaka: