@Quantumboost might be able to help you there also in regards for starting out as a Mage GM.I've got a bit of a question - where would I go to learn how to run Mage: the Ascension revised? Is the Storyteller's guide any good for teaching someone how to ST the mechanical bits or is there some useful website or another that goes over the ins and outs of the game?
In regards to choices that differ mage ST from other games , for one players tend to have a tremendous amount of information avaible to them unless everyone goes full force and they then still can hack a computer at range with a bit of corr. And also deliver rockets/fireballs from out of nowwhere.
Mages are very good at informations, changing the circumstances so that there own powers apply and in certain senses feel more like for example shadowrunners as while preperation is king for them most of them can also don a pink mohawk. Do note that depending on the paradigm on the other hand, some mages are basically unable to cast at combat time unless they went for the pure brute force will effort.
As MJ 12 noted it all depends on what you want from the campaign to give better advices. Mechanically the stuff in the core book is sufficent for your needs as strewn out as it is . Then it depends what you want to play, Wacky astral sidequests require a different book then forging wonders or talismans. On that note if someone has a wonder or a talisman you will require forged by dragons fire for revised as that at least helps a bit with that even if it still has problems.
On the gripping hand one think that I would stress is sit down with the players, at first, talk about what they want to build to prevent decker syndrom and then also take the time to set asside a session after they finished building about what they can do with there spheres and effects now as far to many new players stumble over that roadblock and only tend to think in pure mystical terms or go for the direct application all the time and forgot that for example everyone with force 2-3 can become invisble.Look at this link for example to see some of that.
Tabletop - White Wolf's World of Darkness | Page 49
On the last tentacle based on the link also decide if your game is HOP/HAP/HIP which showcase when something is vulgar, when something is concidental and if it is result or process based
Definitions of Magic and Coincidence is a basic example of the problems with that and showcases why you need to deal with that beforehand.