Reddit reviews New Directions for Clarinet (New Instrumentation) (The New Instrumentation Series)

If you're not familiar with chromatic harmony up through augmented sixth chords and enharmonic modulations, I recommend getting a good modern textbook like those listed in the sidebar.

Counterpoint is indispensable for composers, but the internet is in the habit of perpetually recommending Fux, whose style I regard as outdated. Plus, his examples have contrapuntal and stylistic errors. Brian Hyer's counterpoint manual is fine for species writing. Also look at Seth Monahan's videos on harmonic species counterpoint. Ernst Krenek's manual is decent as a start to tonal counterpoint. Kent Kennan's Counterpoint is a very good book too.

Beyond that, Schoenberg's Fundamentals of Musical Composition and Reginald Smith-Brindle's Musical Composition offer some nice insights to composition.

For orchestration, you can go with Sam Adler's Orchestration, but honestly I usually don't use these books for much more than ranges and this tiny, cheap book is more convenient. Sometimes I'll look up how to notate a certain technique, but even the big orchestration books can be spotty on those and I find myself hunting them down in specialist books. Jazz arranging is a little different. For that, refer to Rayburn Wright's Inside The Score and Bill Russo's Composing for the Jazz Orchestra, but understand that these are built around a certain tradition of jazz arranging.