I've actually never had a dedicated set of robes just for magic; it wasn't ever a priority or a requirement for the traditions I've been and am involved with. I take ritual purity very seriously, so I always make sure I'm wearing clean, nice clothes when I'm doing any working and that I've cleansed myself via praying, ritual bathing, and anointing with oils, and so on. Now that I'm affiliated with the O.T.O. it was time to look towards acquiring some tau robes, and naturally the amazing Ziia volunteered for the task immediately. I commissioned some from her and she did a fantastic job; they're very roomy and comfortable even for asanas. At my request she ensured that the sleeves wouldn't hang too much; my primary concern with robes in general was that they would swing over candle flames too closely for comfort.
Clothing certainly has a major effect on ritual drama. Witchcraft rituals in the nude with nothing but a cord around the waist and a dagger in the palm carry a completely different feeling right off the bat, before even the first words are intoned, from modest, all-linen Kemetic rites. The differences were especially dramatic for the Seven Spheres rituals I worked last year: for Jupiter I must have looked as if I were on my way to a prestigious charity ball; for Saturn, a dreary funeral.
I'm going to consecrate these new robes soon and involve them with my Thelemic, ceremonial, and witchcraft work. I plan on later commissioning a white robe as well.