I use a very cheap oil-filled compass. No base plate, so no declination adjustment. I know what the declination is and correct as I go. This compass is enough for us to navigate through trackless wilderness in alpine and rainforest regions without problems.
Sighting mirrors and all the rest of the frills are mainly to push the price up. Great marketing, but it's your wallet.
OK, why? Because what we do is to roughly align the map with the compass, to within about 5 degrees, and then we compare the map with the surroundings. It has the advantage of working even when you are out of position: when the surroundings do not match where you think you are. (Er, yes, this does happen sometimes...) Then you have to THINK - and THAT is the most important part of navigation - not mirrors etc.
Does this mean we sometimes navigate using the sun and a watch? Yep, all the time. 11 am, sun is there ... north is there, OK, keep going.