Okay, so to weigh in on this discussion a bit, since you said that this would be your first Exalted game, I'd say that as a new player you want to try and have something to do for every broad 'category' of activity you guys might get up to. So, some way to contribute to combat, some way to contribute to social situations, and so on. Probably 7-9 charms in your Supernal Ability, and 2-3 charms in a couple others secondary focuses will suit you well along with the Excellencies you get for your caste and favored Abilities.
Overspecializing isn't bad per se, but it can be harder to play, and if you're a hyper-specialized combat monster and the group ends up going to a diplomatic function, you may end up being bored. Spreading your charms out is less about power for me, and more about staying engaged with the game.
As for other tips: Sorcery is awesome, as was said earlier. Also, 'combat' abilities are not limited to just what's under the Dawn caste skills. Basically every caste can put together pretty decent warrior kit except maybe Twilights. Dawns have all the attacking skills, yes, but a supernal Resistance Zenith is a beast, and an Eclipse or Night with supernal Ride makes a super annoying horse archer. The list goes on.
This next one is from personal experience: Make sure your whole group and the GM are all on the same page with regards to what you all want to get out of the game. Related to that: Keep good lines of communication open between everyone and make sure you guys talk out issues before they have a chance to breed resentment.