Avid book readers of classic and Early Modern English literature have a much wider and expressive vocabulary, and are more likely to pepper their speech with socially-accepted literary references.
But for richer American language:
I especially love the colloquialism, grammar and accents across the American regions. They’re so vibrant, punchy and exciting. This is best experienced in person when traveling and stopping into local restaurants but can also be found in literature, music and social media as well but it requires effort to find which it what makes it fun.
In my case, I ask myself a question like what does a 40 year old blue class worker from New Jersey or a 19 year old Floridian rapper sound like, then the hunt is afoot.
Elites find local speech ignorant but I find it mesmerizing - a radiant, colorful flower in a sea of sameness.