Everyone has different likes, so expect a bunch of replies.
I don't use many sealers, to much scraping and cleaning for engines that will be torn apart every few years, and usually don't need extra sealer anyway.
In general, for gaskets, I put them on clean and dry. Clean the surfaces first with acytone, then install gasket.
Because many of the gaskets that are likely to have issues are valve cover and oil pan. I use blue Loctite on the fasteners and torque to spec. The torque spec is not very tight, so the Loctite keeps the fastner from backing out. Over tightening will cause leaks.
For the main seal, I use the pricy orange one installed slightly offset between block and cap. Use the side seals with a small amount of rtv from seal to block side, and a bit in the corner.
Intake bolts, and bolts that are not blind and have oil or water behind them get some liquid Teflon paste on the threads.
Corners of the block to valley tray get a dab of RTV.
I have been using the combination windage tray / oil pan gasket from jegs. It seals with no sealer. In fact sealer will mess up the seal already molded into the tray/pan.
I use Indian Head gasket shellac on the core plugs, and oil pickup tube to block. also on the outer shell of front crank seal.
Head, main, rod bolts get ARP Ultra-lube.
Been using Royal Purple assembly lube because it is easy to find. Bought some Redline stuff, but haven't used it yet.
The screw-in plugs like heater hose tubes, oil galley plugs, etc.. I just use the liquid Teflon paste on the threads.
I'm likely forgetting some?