#Some caster type with either INT or CHA as the key ability.
Having LA is a biiiiiig disadvantage for a caster-type. Avoid damaging spells which inflicts level dX damages (say, Fireball). Also avoid spells which allows SR. Spells which makes an enemy cry with a single failed saving throw (like Glitterdust) will be your friend.
#Scout, or Scout/Ranger
Skirmish could be your friend as you can inflict good amount of damage from distance. Don't forget to take Improved Skirmish feat in Complete Scoundrel. Having Evasion is nice, too, as you are likely to have very low HP total.
Using a crossbow is a good idea as you are likely to have low Str. Check Crossbow Sniper feat in PHB2. Or, you may throw some splash weapons such as Alchemist's Fire.
Also check Swift Hunter feat in Complete Scoundrel. Scout/Ranger with appropriate favored enemy can use Skirmish against something otherwise immune to it.
A rogue could be an alternative but I do not recommend. In a campaign in which LA 4+ races can be played, you must expect that enemies often have some countermeasures against invisibility. Also, the above-mentioned Scout/Rogue build is much better when facing something immune to critical hit.