As a mystic Adept you will have adept powers and a few spells at your disposal which will empower you to be able to do just about anything. Mystic adepts tend to start comparatively lower powered than most characters, but have (IMO) the highest potential long term.
For your "ninja skills" of B&E, stealthing and hand to hand combat, you will want to focus on the attributes of Agility, Reaction and Intuition. For Magic stuff, you will also want to have a decent Willpower, and I would recommend picking a magic path that has Intuition as your drain stat (assuming you can find one that fits your character with that stat). For skills you will need infiltration and unarmed combat respectively. The skill groups of Stealth and Close Combat might work as well depending on your specific ideals and whether you want to be good at some of the other aspects of those skill sets. I would also recommend Dodge, Perception, and some firearms skills. Depending on how spell heavy you are to start, you're going to need Spellcasting and Counterspelling, and if you're spirit heavy to start, you'll want Summoning and Binding as well.
Other than reading the description for drake characters in the Runners Companion, take a peek at the Core book, Arsenal, and Street Magic. Those are the bread and butter for this kind of character. The core - well, duh, it has all the basics and the primary adept powers and spells etc. Arsenal has extra weapons and gear, and has the optional martial arts rules and, if they're allowed, I would recommend taking one or two ranks in one or two styles from there. Street Magic has some awesome extra adept powers for being the B&E ninja type, and has some other interesting mojo related stuff - including a host of new magic paths.
After doing a wee bit o reading to familiarize yourself with the character you've been handed, feel free to come back with a build and we can help you out.
And lastly, I would highly recommend looking through the other character builds in this forum to help you get an idea for how this works and what a finished character build should look like. Looking at other peoples work can be really really helpful.