Methylene blue has a lot of awesome uses but it will kill your biofilter. so it is not something you want to use regularly. It will also stain your decor, wood, and silicone blue and turn your water blue (pretty, but makes it hard for light to penetrate). It's also toxic to your plants.
Your best use of it is in a hospital tank if you need to treat some fishes there. A hospital tank doesn't have to be fancy, it could be a plastic bin if that's all you have, although it needs a simple filter and a thermometer.
I can't think of a lot of reasons I would add methylene blue to my display tank, though. It would really wreak havoc on the ecosystem in there.
All of this sounds like I think methylene blue sucks - not at all. I am using it now in a hospital tank. I just don't think it belongs in a display tank, unless ALL your fish are sick and need it.