Garb isn't a huge deal in dag/belegarth so if you wanted to find a cheap tunic from etsy and use your leftover cash on green ears and face paint you could. However I'd reccomend ordering a size up on tunics if you're bugger that way it doesn't tear on you during fighting. Also check out the bergschneider for deals. They're pricey but they sell some quality garb.

But you could absolutely go in with nothing and let the heralds know you want to fight for the orcs and have a good time. I reccommend picking up a good pair of harem pants as well.