This is depending on what you really like, let's see which of the outfits were made "for paladins":
If you're simple and want something cheap go for the classic one ahhh who doesn't love classics?, the hunter outfit:
If you miss the old days oh man the retro hunter outfit one is for you:
If you like the gothic theme then the Sinister Outfit is for you:
If you feel like a real veteran of the paladin clan then you will love the Veteran Paladin Outfit:
And by the last one and in my opinion the best the Ranger Outfit:
And for the mounts you should choose the coolest one for sure, in my opinion are this:
Neon Sparkid
Sparkion
Crimson Ray
Toxic Toad
Leafscuttler