Angel, no doubt. He's always been my #1 identification figure on the shows, regardless of gender!
I can also see bits of myself in Buffy, Fred and Wesley, but Angel is easily the best identification figure for an Aspie who has struggled with low self-esteem, depression, self-doubt, introversion, social anxiety, self-isolation, being stuck in the past, inability to read social cues, making connections, a suicide attempt, pessimism/realism and constant fear that one has done something wrong, has failed or isn't good enough. However, at the same time, he's also an inspirational figure for a person who has had such struggles, because he's always shown trying to get back up again after falling down, trying to make connections despite feeling he's going to lose all of them and still having hope.
I also heavily relate to his love of languages, travel and history, which are major interests we share. One of my biggest draws to immortals in fiction has always been the living history aspect.
I'm pretty much a walking textbook with legs of useless, specialized factoids who gets teased and mocked for it, so that part is also Wesley on top of the many traits he shares with Angel. Angel's memory is another similarly relatable trait.
And my relation to Fred is specifically the crazy Pylea version. Her speech in Fredless echoes my own experience almost eerily of being stuck in another country (Mexico, in my case--I was at a tough-love program, which was shut down for child abuse, called Casa by the Sea run by WWASP after being bullied so bad I had no self-esteem when my Asperger's was still undiagnosed) without being able to communicate with my parents for 10 months and then coming home to build myself another cave that only I could make the choice to come out of.
And I have a similar backstory to Buffy and Angel of losing all of my fake, so-called friends (in school) and becoming a social pariah. I also have a very girly side and a prematurely dead parent I felt guilty about not finding in time (my dad had a stroke on the staircase while I was asleep and died three days before my 30th birthday), so those are more things I have in common with Buffy. You can also now toss in utterly horrid events associated with a birthday.