3.5 Aasimar Swordmage - trying to make something similar to sephiroth

[Senevri]

That's not very sephiroth.

First level elocater dip is very post-nuts sephy, as he tends to float everytime you see him.
Beyond that, Wilder or Warmind or PsyWar all can be made to fit.
Maneuver-wise, I see sephy mostly as a diamond mind/divine spirit type. Maybe some Desert Wind - or emulate blasty stuff with Psionics?

Not sure what the optimal mix is --- you need IL 17 for cap maneuvers, but they aren't that uber. Diamond Mind is fun, though, but it's more of an omnislash thing.

I need a list of psionic prcs...

[Maat_Mons]

psionics are a great idea

I think the “standard” psionic gish is ranger 1 / ardent 4 / slayer 10.  That puts you 2 levels behind on manifesting and 1 level behind on attack bonus.  

part time skill monkey

ninja-samurai

For being a substitute skill-monkey and adding a ninja flavor to your character, ask your DM about the option to allow aasimars to qualify for human-only feats, from Races of Destiny, page 150.  This seems especially appropriate since you will have the humanoid type and will have spent most of your life as a normal human.  Supposing he agrees, you can take the able learner feat from the same page.  

Able learner, the skilled city-dweller alternate class feature, and the build above get you hide, jump, listen, move silently, search, sense motive, spot, and tumble as class skills for all your levels (essentially).  That's pretty ninja-ish.