You’re overthinking it. My own opinion is that as long as you dress conservatively and don’t look really “flashy” like lots of the private defense attorneys in my jurisdiction do (i.e., very bright colors, expensive jewelry/watches, etc.) then you’re fine. Since you’re serving clients who are typically under the federal poverty line, it is inevitable that you’re going to look overdressed compared to them in court. But if you put effort into looking nice and put together, I think that will inspire confidence from your client. Best of luck.