Definitely dust collection - top of the list, choose from the following a cyclone extractor (wish I had bought one of them first of all)a shop vaca dust deputy for the shop vac.a Trend Airshield Pro - they are superb and keep all the crap out of your lungs.an air cleaner to hang from the ceiling,a shop broom,a hand brush or twoand a dust pan to collect it all in.plenty of strong plastic bags to take it all to the dump Oh and then buy some tools
If you do decide to use a varnish finish in the bathroom I can recommend General Finishes External 450 as being superb. It is designed for outside furniture and is waterborne. I have used it on a couple of internal furniture bathroom vanity projects and after a few years does not show any sign of deterioration due to condensation or direct water surface pooling. It does have an amber element to it and it enhances the grain of wood.