If you are going to put Jinx in, I would only run one or two. You are only trading one of your quick actions for theirs, and at a cost of 3 mana to you as well, so you want to make sure that quick spell you prevent is something that's going to cost them THAT turn that they use it. I think in our game, it could have stopped me on certain turns from escaping, or putting that curse on you, but it still would have put the spell back in my book, and refunded the mana I spent on it, which is weird for a "counter spell".
Jinx is good, but for it to be awesome, you have to be a bit of a mind reader. I like to jinx the same turn as I play mage wand or some good equip because you can pretty much be certain that a dissolve is coming your way. Jinx either stops that from happening, or forces them to play two spells to your one. Just an example of "when to play Jinx" from a noob like myself. I'm sure others will tell you how bad or good Jinx ACTUALLY is, but it has its perks to be sure.
Just my experience with it. I usually only use them with my Wizard books, but that's only because its not a novice spell, and I feel like putting more than 2 in any other book is a waste of spell points. Even as a FM, I feel like its not a bad card, but there are probably better options. I have never played a FM, so I may or may not have the slightest idea of what I'm talking about. Take that as you will.