50mg was my dose before I got a more efficient method of vaping, before I would use a pipe or bong and hover the flame just above the material. A lot probably gets combusted in the process, hence it is not as efficient as a good vaporiser. 50mg in the VaporGenie would probably make quite a mess of me if I was to vape it all successfully to be honest. I would start lower if you are going to use a vape personally.
The VaporGenie is absurdly efficient so you need a lot less to get to the same place. It is different to other vapes as it uses a convection heat source (the hot air flowing through the material) rather than the direct heat method of conduction that most vapes do.
If you have a search about some people seem to like a cheap homemade device called The Key as a budget alternative to the VG/GVG, may be worth having a look into (the VG/GVG are quite expensive). I have yet to try it though, so I can’t comment too much on it.