Hi!
I'm still new to the Dresden Files RPG and I'm still trying to figure out which power level we're starting with. My problem is that I would like to start with weak characters so the players will get to know the world from a horror point of view. But over the course of adventures I want them to be Were-thingies, Wizards and Whatnot. While I could see someone going from a minor talent to a sorcerer to a wizard. It's less likely to go from a Red Court Infected to a White Court Vampire. On the other hand, I don't want them to start as pure mortal (except for those who want to 
)
So my question is how would you start strong templates as weak characters? And another one is, are you able to make a radical change to your character later on? E.g. going from pure mortal to wizard? Is this possible with character advancement?
Thanks for your time 
There really isn't any way to go from Red Court Infected -> White Court Vamp though (They're two different Beasts entirely), the only exit (leaving out GM handwavery) for a Red Court Infected, is eventually giving in to the hunger and becoming a full Red Court Vamp and an NPC. (It would be interesting however to see what would happen if a Red Court Vamp bit a White Court Virgin though...which nature would be dominant).
There's nothing to stop you going from pure mortal/focussed practitioner to Wizard, or from White Court Virgin to full White Court Vamp, the PC just needs to pick up the extra powers as they reach major milestones and alter their aspects to reflect these changes.
In such cases I'd ensure that there is some in narrative justification for this development, particularly where a Pure Mortal gains supernatural powers, whether this is discovering that his great great grandfather was a demigod, or learning to call upon the spirits of the dead for aid, it isn't something that should just happen without warning. Maybe that burgeoning necromancer gets the feeling of being watched when investigating a notorious murder scene, or sees flickers of movement just out of sight in a graveyard, maybe the second cousin twice removed of Zeus has occational boosts of strength during emergencies, put down to the adrenaline rush of the situation.
This can be easily done through the "Temporarily acquiring powers" mechanic that I believe is to be found somewhere in YS (the page ref escapes me atm, but I'm sure that someone knows).
If however you want characters that naturally progress as a part of their template then Scions/Changelings are good bets, and you could even start them off as pure mortals, unaware of their heritage who are naturally rather shocked when some traumatic event triggers that spark of inhumanity within them.
Edit: Tracked down page number for the 'Temporary Powers' mechanic it's YS pg 92
