Battle Blessing is a must-have, since it seems you're starting out at level 10 and at level 11 you start getting 3rd level spells, many of which are awesome. I'd suggest NOT giving up your mount, since a number of the best spells are either specific for the mount, or amazing when shared with it. For example:
Righteous Fury is just ridonculous. I'd also suggest taking Practiced Spellcaster...
Yeah I know... in a game devoted to hunting spellcasters, I'm suggesting a lot of things related to spellcasting... but that's because in D&D spells are king... and this is the best you got (luckily paladin casting actually isn't that bad, especially with Battle Blessing.
Another pair of insanely good spells are Heal Mount and
Call Mount. The awesomeness of the second one (which is only 2nd level, and so available starting out) is not 100% apparent... until you look at the casting time, and also the action required to dismiss your special mount. Then you realize that when your mount is low on hit points, you can 1) dismiss it as a free action, 2) resummon it with full hit points as a swift action, then 3) remount it as a free action and still make your full attack/charge/etc for the round...
While not 100% kosher/clear, I'd ask the DM if you can "share" the Shield Other spell with your mount... and cast it with yourself as the target. Then (hopefully, depending on interpretation), half of your damage can be "soaked" by your mount, which you can dismiss and resummon as a free+swift action with full hit points.
Make sure to get everyone in the party to worship the same deity so you can get very good healing out of 1st level spellslots (and wands) with the
Faith Healing spell.
