I have both Burn and Mystique so let me give you some advice.
They are both incredible. Both of them include incredible tricks that could very well shape your routine. I literally have a Burn Deck (some of you might say it is not advisable, I don't know, it just kills at parties), which I use with a lot of the Burn Gaffs. Burn Gaffs are not really "easy" to make but if you have the right materials (if you do not, you can buy it for about $3) you should get it down in half an hour.
Mystique also has a lot of great tricks such as Angle Zero, Breach, etc. They are great, but a lot of them require some sort of setup, you could not borrow a deck and do all those tricks without any alone time. That being said, you can't do it with Burn either (obviously)
I would go for Burn because (if this is exposure a mod can delete it), for one thing, Angle Zero is taught on Burn. It is one of the best tricks on Mystique, and it is taught. Although it isn't taught as well, you will know the method and your imagination of the presentation will carry you through your performance of it.
But if you can, get both.