Based on your listed preferences, I think you might like Sage the best. A wizard would be good too, but I don't think they solo so well, and of course no healing. Once Sages turn Mystic especially, they quite often sell dungeon leeches to other players, because they are very good at soloing.
A sage IS a more complicated class to play, however. So depending on your gaming experience, I'm not sure if you'd like it as a beginner class. It has 3 animal forms, and to be really good you need to be able to switch between forms as needed. Different forms use different weapons as well, so you'd need to be able to switch weapons quickly too.
Clerics don't put out as much damage, but they are a good, strong class to play as well. IMO they are the strongest of the magic classes. They can use a staff (I use it in parties when I'm the healer), or hammer and shield (I use when I'm killing mobs or soloing). They take longer to kill something, but the enemies have a harder time touching them, between their higher defense and knockback skills. Even if they aren't going to solo a dungeon, a cleric is ALWAYS wanted for dungeon parties because of their buffs and healing skills. The major disadvantage to cleric is their damage output is slower, but it's not as slow as many people would lead you to believe. If you round up the mobs, then use your aoe spells, then you can kill nearly as fast as the other magic classes.
If you're willing to give up a little on the healing, there is necromancer. Although they can't actually heal themselves, they do have two spells that accomplish the same thing almost. There is drain life, which damages the enemy and gives a percentage of that damage back to you as healing, or there is a spell to draw life from your summon to heal yourself as well. In addition, you can use your summon as a personal tank with some practice, so they will take more of the damage instead of you. They don't have a knockback spell, but they do have Magic Star Cannon, which makes the mobs dizzy, or they have a fear spell that will send them running for a short time.
I have all three of those classes, and they are all fun to play. Which one you pick just depends on what is most important to you. For a guardian sprite, I'd say if you are able to get a legacy set, then go for a weapon sprite (maybe staff for all three of them, since it seems to me to be harder to find a GOOD staff sprite). If you can't afford a legacy armor set, then get an armor crafting sprite. The sprites make MUCH better armor than anything you'll find at the shops or dropped by mobs. For the healing classes, you need p-equip sprites, for necromancer (or wizard) you need m-equip sprites. As long as you get a guardian sprite that is in someway useful to you, it doesn't matter so much which of these you pick. You can easily find wild sprites to fill out the rest of what you'll need.