So I am a level 5 path of the ancestral guardian barbarian. Due to role-playing and story I multiclassed into Paladin. However I am fighting with myself about how many levels I should put into each class (this will be a level 20 campaign). I really like the 14 level feature of ancestral guardians. But I'd also love to have a bunch of smites. I definitely want to take one more level in barbarian to get Spirit shield because it works so well for my character thematically. What would you recommend for a level split?

As few levels as possible because that way you access the other's higher level features sooner.