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 