Supporting Cast/Guest Stars (ie. NPCs)
There are a few options for "purchasing" NPCs, depending on how you want them to interact with your character. Mostly you just make 'em up and add them to the narrative; you only have to pay for them as a Quality or earn points for them as a Drawback if they have a mechanical/noticeable impact on your character.
Dependent is a drawback that indicates that 1 or more people are, well, dependent on you for basic needs, like a child or ailing parent.
Contacts is a quality that lets you define a relationship with an NPC or group of NPCs who is/are willing to help you within a certain scope (to varying degrees based on what you spent on the quality)
Also, The Magic Box supplement and the Angel Corebook have rules for building organizations, such as law firms, witches' covens, gangs, etc.. that you can take as a quality or drawback (depending on the requirements of the group) that can give you more direct benefits than just contacts.
So, for example, Rory could have Contacts (Local Entertainment Industry) 1 that he can use to learn about insider information on local events (to find the demon hypnotist's next show), or we could build a group for Rory's band with various requirements/benefits like must help band mates, can share occult books, +1 Art when performing together, free helpers for ritual casting, etc.., and thus his band can have a mechanical effect on him.
Combat
Combat will definitely feel more fun if you just kind of go with the flow and describe your actions. There are a lot of different combat maneuvers should you wish to employ them, but it is likely that over time you'll find 3-4 that you feel fit your character best and just fall back on them (that's not a requirement, just an observation I've made). Stand-bys often inlcude punching, kicking, staking through the heart, crossbowing, biting (for vamps), magic-y-ing (most spells are too slow/time consuming to be used in combat, but character with the Sorcery Quality can "quick cast" certain spells, which renders them combat-available.
The narrative idea will help too with the way combat is resolved. Initiative is rolled the first round (d10 + Dex), but for every round thereafter, initiative is won by Narrator/DM fiat (ie, whomever he feels is in the "advantageous" position at the time - ie, if you spun around behind the vamp last round, you win initiative because he's slighty off-guard)
Each round has all characters involve declare their intended actions, and then those actions are resolved in initiative order... assuming an earlier action doesn't negate them. Characters typically get 2 actions per round (and often use one for an attack and the other for a defense like Parry or Dodge but not a requirement), but high Dexterity can yield more actions (don't have chart handy) at cumulative penalties to any rolls.
[sblock=example]Combat Example (sans actual rolls cause I don't have the modifiers here)
Spike and Giles are debating the pros and cons of rugby league vs rugby union while patroling, when two vamps jump out of nearby windows, declaring death for the vamp who hunts his own kind.
First Round:
Spike: Bugger this. I'll whip out a crossbow and peg one through the heart, and since they don't look like much more than nancy-boys, I'll use the crossbow to parry one attack, but then use my extra actions to reload and fire again, in case I missed earlier.
Giles: Goodness. I draw a stake... no, I'm already carrying one... alright, I'll approach with my guard up, and give him a right jab as he nears.
Both vamps show their game faces, and rush the two Brits, one trying to grab Giles and throw him into Spike and the other trying to tackle Spike.
Resolution: Spike wins Initiative, then vamps, then Giles.
Spike rolls well with his crossbow, dusting it easily.
The remaining vamp grabs Giles before his punch is thrown, and with supernatural strength, hurls the tweed-clad missile at Spike, knocking both the the ground.
Giles is in no position to punch the vamp now, and loses his action.
Round the second:
Spike: Get off me, wanker! I'll fend off any attack on me, then sweep the vamps leg, and stake him.
Giles: I'll roll free, full defense, letting the vampires finish this.
Vamp: I'll teach you to consort with the chattel! Grab Spike by the collar and throw a few rabbit punches.
Resolution: With both Giles and Spike on their backs, the vamp wins initiative
Even on his butt, Spike is too skilled (and the vamp rolls poorly), failing to even grab Spike's leather jacket.
Channeling Cobra-Kai dojo, Spike sweeps the vamp's leg, dropping it on it's back, then uses once of those fancy Angel-esque stake poppers (patent pending), to drive some pine into its chest, dusting it.
Giles, relieved at not being knocked unconscious, celebrates y wiping his glasses.
Combat over, Spike checks out his smoke, sees it damaged, curses, then draws and lights a new one.
Spike: Rugby league... Next you're going to declare Leeds better than Man U...[/sblock]
One standard op deviation for Buffy RPG from D&D... it is not always foolhardy to be off by yourself. Sure, you don't want to wander the cemetery with a big "come bite me" sign on your lonesome (well, except maybe the Slayer and/or Rechard when on the hunt), but Rory can head off to a gig generally without fear of being jumped, or Dafydd can stay in his lab doing research without being threatened. While yes, this game is working on the axiom that demons, vamps, and the like exist, the game is set in a modern day city, so they're not hiding around every corner, or even every second corner. If semi-reasonable precautions are taken, chances are, you'll be safe, or there's a good reason the big bad risked campus security and broke several locks to find you studying in a classroom.
Corollary - not everyone needs to be physically involved in every fight. I try to make sure there's always stuff for people to do, and sometimes that means there are extra vamp minions around for the white hats to occupy while the big guns battle the baddies, but sometimes it's the Slayer who is just doing minor demon control while the magically-inclined work their mojo against the spirit world.
Corollary the second - that said, part of the fun of the game is throwing people into situations they're unprepared for - the technophobe Rechard needing to repair a robot, or the Slayer (well, not Shayuri's nerd slayer, but say... Buffy or Faith) needing to pass a pop quiz or be held in detention and miss the fight to stop the Apocalypse (not that Faith would stay, but...). Sure, it won't happen all the time, but just like the violence-inclined may need to use nice words on occasion, the violence-adjacent may need to curl the fingers into the fist once in a while.
Appendix 1 - Also, if you are in a situation where you feel overmatched, remember your Drama points. They can add +5 to a roll, which is useful in a pinch, but for the creatively minded, they can be so much better - example: the seductive, and surprisingly husky, fem-vamp has Dafydd pinned to his seat, all ready to take a savoury taste; knowing he's not really in the vamp's league violence-wise, rather than adding +5 to his Dodge roll to avoid the attack, he uses his Drama point to have local delinquents choose that moment to pull a fire alarm prank, and all the sprinklers going off seriously wigs and distracts the vampire from her task, allowing Dafydd to scramble behind his desk... Note it won't completely swing the combat, but it will throw a definite wrench in there, perhaps allowing other opportunities for survival
Clear like wall?