Paladins can switch spells. So if you know your fighting a green dragon, then yes, you can prepare it for the day, but your likely going to drop it for the next.
Many days you can run into foes with poison though. I am presently playing a 6th level Devotion Paladin, who already gets oath spells of Lesser Restoration and Zone of Truth, and there are limited second level spells of value otherwise. I take Aid, and you don't need Find Steed every day, so I am including Protection from Poison with some frequency just in case.
I am also using Shield of Faith regularly, because the first round I am using a standard action to charge up the sword with the devotion power, so then I use the bonus action to cast Shield of Faith, and then use Shield Master for bonus thereafter. And because the Shield Master uses the bonus, I am not particularly interested in any of the smite spells that use it as they take bonus actions to cast and eat up concentration slots even if you immediately hit, just seems better to add them as smite damage. Further, Shield of Faith has worked out to be about a 2nd level Cure Wounds cast in advance as a bonus action for the amount of damage it has saved on average from those swings that miss by 1-2 points.
While Bless is great, since the devotion takes a round already, I do not often see myself spending a second action to set up Bless as well, though perhaps Bless can be a backup to use the first round when there is a second combat before a short rest and the devotion power has not recharged (which is extremely rare as we are playing Red Hand of Doom and it is a lot of once a day scenarios with overland travel).