The Paladin Seal/Judge system of combat is poorly thought out and a pain in the butt. Multiple Seals that can have different effects on mobs when Judged looked great on paper, I'm sure, but fail in game and is a major reason why people don't like playing/leveling a paladin. But enough ranting.
40-50 is a rough time for Paladins, mobs get significantly stronger while every other class gets to try out their new "toys" (i.e. Mortal Strike/Bloodthirst for warriors). We get....
I'm assuming you are using Improved Sanctity Aura, which is a good choice, the other option is Retribution Aura. Your blessing is good, the only real choices for a leveling Ret Pally are Might, Kings, and Wisdom, and Might is the best of the three. For mana issues, don't Judge Crusader. As a matter of fact, don't Judge. It's a small dps increase for a large mana cost. Just use Seal of Command.
Oh, and one other thing that many people don't know, Rank 1 SoC does the same amount of damage and has the same chance to proc as Rank 6 SoC, the only difference between the two is the amount of Judged Damage. Huge mana saver there, just drag SoC rank 1 out of the spell book. Keep the faith and keep plugging away at it, level 50 comes soon and then you get Crusader Strike, which is just plain awesomesauce.
As for gear, just gear you Ret Pally as you would gear a warrior, "Of the Bear" is your friend.
This is just my opinion, but I leveled my Prot Pally as Ret, and am working on a 2nd Paladin Horde side (Level 64!).
Forth, and fear no darkness! Spears shall be shaken, shields shall be splintered! A sword day...a red day...ere the sun rises! Ride for ruin and the world's ending!