There are parts of my Larp Costumes that people never see, armour and overcoat cover it all. The grimy shirt has one purpose only: To protect my undershirts from the scalemaille mesh. The black dirt is from the armor, and I do not bother with cleaning it off every time, since it gets like this as soon as I wear the scalemaille. Only the collar, sleeves and lower hems can be seen beneath the armor.
The linen undershirt is my most recent one, and it uses a new base pattern I made. Collar, sleeves and hem will peek out under most outer layers, so I added some embroidery to them.