If you're going to be a paladin/sorcerer the best bet is paladin2/sorcerer4/spellsword1/abjurantchampion5/sacredexorcist8
Feats:
1-power attack, combat casting
3-knowledge devotion (the planes for your knowledge skill)
6-practiced spellcaster
9-arcane strike
12-minor shapeshift
15-divine might
18-whatever
At ECL 13 you'll be casting as a 11th level sorcerer and I'd recommend the following spell list:
1-shield, grease, silent image, protection from evil, charm person
2-glitterdust, wings of cover, resist energy, invisibility, web
3-dispel magic, haste, greater magic weapon, stinking cloud, phantom steed
4-greater mirror image, wings of flurry, orb of fire
5-dismissal (for sacred exorcist), draconic polymorph
Lots of swift/immediate actions spells with plenty of buffs, spells that target all 3 saves, and just a little bit of debuff, blasting, battlefield control, and utility to round things out.