so Im new to D&D and I wanted to make a black dragonborn wrarlock pacted to the great old one. what would be the best stats to have. Im switching from a level 3 half orc fighter so he should be level 3 and Im going with the tome pact.
I can't remember if they use point buy or the standard array in AL, but either way I recommend Charisma, followed by Constitution, and then Dexterity. Wisdom is probably more useful than intelligence or strength in adventures, so consider putting anything left over into that.
However, I believe you should have asked this in either the Adventurers League or the Character Optimization subforums. The people who frequent them tend to be a bit more knowledgeable in such things.