So here is the basic problem I'm having; after doing some work in my living room (not electrical or structural, but used a drill and was vacuuming to clean up - a contractor was doing work in another unit but I don't think that made a difference) the ceiling lights and two receptacles failed, while the rest of the circuit (it serves the dining room, foyer and one corner of the kitchen, two unused receptacles and the range which is gas, so really only the clock) was fine. I've narrowed down the likely location of the break in continuity and decided that this is a prime time to rewire from there since the wiring is the original (I assume) from when the building was built in the late 20's and there are ancient taped splices which are probably suspect as well. Eventually I'll split off the kitchen receptacle since it's nearly back to back with a switch box and the wiring there is wonky circa 1960's kitchen renovation work.

So here's my basic question - which gauge wire should I use? From all I can glean, 12 is the way to go for receptacles and I will eventually tap one of the receptacles for another (all walls are masonry so I can't do that myself) and the ceiling lights are vintage with 5-bulbs each so that seems reasonable there as well.

Thoughts?