Buffy and spike meet at a party but don't know who each are.
I think Spike is Master of Los Angeles or what ever city it was placed in.

Could it be the Arena series by Kismet?

https://www.spikeluver.com/Forum/index.php?action=vthread&forum=2&topic=296

It was looked for before and I read it back then the links are on this page.

Hope to have helped you

found it or something... ^^

masquerade by bittenandstaked

http://web.archive.org/web/20050416154632/www.talesoftheslayer.com/masquerade.htm

Spike is prowling a masked ball being held for the locals of Sunnydale when he finds himself drawn to a young blonde girl. As they leave the party they realise each others true identity but will this stop their masquerade?
Spoilers: Roughly set in Season 1.

Nope. Neither. But I've read those two. Spike is leader and thereis a part where he orders other people around.