How does levelling work when playing a character with level adjust

[evangaline]

Greetings,

Let's say that I am a halfdragon spellthief 1 with +3 level adjust. How much xp do I need to level up?

[Lightlawbliss]

you are ECL 4 so you need the xp to get from ECL 4 to ECL 5 minus what you have.

[Valluman]

you are ECL 4 so you need the xp to get from ECL 4 to ECL 5 minus what you have.

This. When you start as a level adjustment, such as your three and your level one in a class, then you have the experience of a level four character.