Paladin spell and feat progression
This is the last version of the detailed spell and feat progression that used to be on the Paladin new player guide, created by Isharon and expanded on by other players.
The order takes into account spell slot costs and expected (minimum) magic ranks for each circle, indicated in the far-right column. You may be able to use spells and feats earlier than listed here. If you have the magic ranks to cast Divine Armor, Rutilor's Edge, Holy Warrior, or Truffenyi's Rally earlier than indicated I would learn those spells sooner. (See this table for rank requirements.) Similarly, I would learn the feats of Deep Attunement and Efficient Channeling as soon as possible
General Progression for Training and PvE
This is a general-use setup for Paladins who primarily enjoy PvE. If you enjoy PvP, your choices may vary. For training purposes, this choice gives you access to all five magic skills as early as possible.
How you spend your final slots is really a matter of personal preference. The mastery feats are useful, because they let you channel more mana into spells than your skill would otherwise allow, and when you outgrow them, you can unlearn them and re-allocate those spell slots. If you are nosy, you may like the Basic Preparation Recognition and Advanced Spell Knowledge feats. These reveal what spells people are preparing around you.
The research feats at the end of the list let you add a single stat or skill buff to any of your standard spells, greatly increasing the challenge of casting. (This is good for training at high levels.)
If you want to practice Sorcery, you will need the Magic Theorist feat, and you may also want to invest in Sorcerous Patterns to reduce sorcerous backlash. (Without this feat, if you follow the progression below, you can only use other holy mana spells.)