Basics are per M20 core, feel free to use G&M and BoS stuff.

Some specifics:

Factions/Sects: Dissident Technocrats, Disparates and Traditions only at the moment. NYC is wildly diverse, so we'll try to work with you. Technocracy Reloaded may see the introduction of Techies proper into the game, if it can mesh with the setting. Nephandi are flat out for reasons that shouldn't need mentioning (you can be a huge bastard without needing to want to make the cosmos eat and fuck itself at the same time).

Attributes at 1 will need justification, especially if there are no Flaw purchases involved. Attributes over 4 likewise. This is just a 'hey talk with us to work something out' thing, not a big deal. Enhancements and Advantages can make these weird, and with justification, that's fine.

Secondary abilities and the specialization they offer make sense for the sorts of characters likely to Awaken or achieve Enlightened use of the sciences. At creation, they are 2 for 1 dot, but cost the same in freebies (i.e. if you buy 3 dots of Underwater Basket Weaving and 3 dots of Miming for whatever reason, it only costs you 3 dots off your total. But the fourth or fifth dots, should they be purchased, are bought with freebies per normal).

Try and keep Merits under 10 points. I know there's a lot of fancy stuff, especially with Book of Secrets out, but so much of it can be had in-game. This does not apply to Languages, you can go nuts with those. In fact some concepts rather require it.

Enhancements and Advantages are up for purchase if you have the appropriate character background. Permanent Paradox and other surprises should be expected.

Backgrounds above 3 will be questioned.

Backgrounds above 5 will not happen. NYC is a city in crisis among the Awakened, and their connections are powerful, but not as world-shaking as they would be in a more stable setting.

Banned/Restricted Merits and Flaws:

Avatar Storm stuff and True Faith are off the list. Avatar Storm is someone else's setting, and True Faith is a bit redundant, if not flat out silly.

Venue-crossing stuff is going to make your life more difficult, and everyone else's, so don't. You can make those mistakes in character if you really must.

Child. This is gonna get weird, let's not bring kids on the acid trip okay?

Pretty much everything else is case by case. Mages are individuals, powerful ones, and their journey is strange.