Just a ubacs and a chest rig, or plate carrier. Im setting up another loadout wich is just a ubacs, coat and a belt/harness. Either is fine, as i will hear or feel the hits. The carriers and rigs are really more for load carrying and looking tacticool than any protection, as i find i always get hit somewhere else anyway lol
Just a few layers should do it, thick t shirt and fleece or hoodie. Unfortunately it also depends how well (or not) you bruise.