Marketplace is active. Also depends on what you want to do. Sounds like you want to do Magic. Not too sure about that arena as I've only have two cardistry tutorials.
A lot depends on the time at which they are released. Around the December Holiday Wheel is god, but a lot of people have the same idea, so your tutorial mught get quickly shunted off the first page within a couple weeks as opposed to the othert 11 months of the year where your turoail could be near the top for a while.
Also depends on price, how much you promote it, where, quality of tutorial, testimonials from others.
As said earlier, do not expect to rake in a ton of cash. It's best if you put what you do out there and not think about it unless you're trying to build a sizable reputation and need to promote your material a bit more aggressively and more frequently.
But do try to promote your stuff around the Holiday Wheel, I will say that will help.