While I certainly advocate the use of robes for a baptismal/chrismation service, or perhaps a dress in the case of women, these are "lower t" traditions, as was remarked here. Wear what is all at once comfortable, nice-looking and, preferably, a light color.
I did not have the luxury of a baptismal robe myself (and I was accepted into the Church by baptism). My priest's instructions were to come in something dark, and so I wore black pants with a very dark blue shirt and then change into light colors after the baptism, and so I changed into a white shirt with very light khakis. Of course, shoes were not worn since the neophyte stands in the water and is twice anointed with oil (once, if just being chrismated) and then has the chrism wiped off later, on several parts of the body, including the feet.
And, for the record, I don't know your background pre-Orthodoxy, but Antioch generally leans more towards economia when receiving Christians from other backgrounds. If you were baptized at some point in the name of the Trinity, chances are you will be chrismated only. That said, I can't know for sure, but I have quite a few friends in the Antiochian Archdiocese and I'm fairly familiar with their practices.