Best sorcerer subclass to multi class with paladin.

I plan on playing a level 19 oathbreaker paladin and level 1 sorcerer. What’s the best subclass for the sorcerer part to be?

(I didn’t know if I should put this on sorcerer or paladin so I put it on paladin)

None would be my suggestion.  The whole Paladin/Sorcerer multi-classing is tired, cliched and lazy. 

I would suggest whichever one fits the character but it is unlikely this is a concept driven build. 

A one level dip won't give you much, I don't think they even get any meta-magic until level 2, so pick one at random.

Metamagic happens at level three, so a level in sorcerer doesn't do much beyond making you miss the level 20 subclass capstone.

It could probably be fun to combine say, oath of the crown or devotion with clockwork sorcerer. "There's a time and place for everything, that is the holy order of reality and those who break it must be set straight".