Reddit reviews Selected Studies: for Trombone (Rubank Educational Library)

That's what I mean. My suggestions are probably within your skills, but you probably don't know how to interpret and adapt a solo to your abilities yet. Not putting you down, but any collegiate level audition piece suggested needs some coaching.

Start with a Rochut exercise for your legato, but I don't know what solo is within your ability.

Perhaps you should look at the Voxman Selected Studies for a start. You might even consider picking up the baritone book for that price, as well. Either way, I truly believe you would benefit greatly by sitting with a local trombone teacher and discussing this between yourselves. Moreso than asking a bunch of strangers that have never heard you, and you don't know our qualifications.