To get a Genie: go to the Watcher of the World in any major city and either buy one with 3 mirage celestones, or get one with "Quest Related"
To Level you Genie:
equip it in the slot in your inventory
right click its face, choose EXP infuse
check if you want to use your OWN exp, your OWN Spirit Points, or an EXP cube
EXP cubes are given from quests, and at Watcher of the World
Click and hold the "Infuse" button to give it some of your OWN Spirit or Experience points....yes, it requires your spirit or exp points to level a genie.
If you're impatient, just hit the "Level Up" button and it will automatically infuse all the needed EXP or SP (whichever you chose to use) to get to the next level.
OK, first off I cannot say that I am 100% sure on any of this...this is simply my take on the whole Genie system so far, and how you should/might want to build yours.
First off let it be known that Genies are basically a money and exp pit. They take your exp and/or spirit points, and cost money to use (they require chi stones to function...which have skyrocketed in price as of late because of the Genies). Without chi stones (aka the stones you used to give your flying mount/sword/wings more "Haste"), the genies will have no Stamina. No stamina = no spells.
As much, Genies are not terribly useful in solo PVE (Player vs Environment...killing mobs for quests). The cost to benefit ration is too high at this point with the cost of chi stones. As well, it takes a lot of your exp points and/or spirit points to level them up...making it take longer to level your character.
Now, with all of that being said, lets get down to the nitty gritty: building your genie.
As of right now I am unaware of any differences in the availability of spells between the Genies, save for the first spell it comes with by default. From there, the only difference is the attribute points they come with by default. Here's an overview of what the are:
White Genie (Discipline): has more Vit by default. More Vit = greater maximum energy for the genie. More energy = more spells can be cast.
Purple Genie (Infliction): has more Str by default. More Str = greater dmg done per spell.
Green Genie (Longevity): has more Dex by default. More Dex = greater range, duration, and success rate of the spell. Success rate refers to some spells having a "chance" to do X. More Dex = greater chance of X happening.
Orange Genie (Zeal): has more Mag by default. More Mag = greater energy recovery rate, and greater number of spells able to be learned.
Now, the first step to building your Genie is to figure out what you want it to do for you. This is all assuming you will be focusing on having one Genie. If you are going to level more than one Genie, you can have each Genie perform specific tasks for you. We'll be assuming one Genie for each character here.
So...determine what you want your Genie to do for you. Do you want it to attack things? Heal you? Buff you? Purify you of debuff's? It's all up to you. While you can make a more "rounded" Genie, it will only mean it will take longer for your Genie to be useful. Personally, I'm impatient and want a specialized, badass Genie for PK and PVP (which is where Genies are more useful, remember). So if you want you Genie to hurt shit, give it more Str. Want it to know more skills? Give it more Mag...etc etc.
Once you've figured out what you want you Genie to do for you (Heal, Attacj, etc), you have to go through the skill list and find the spells/skills that compliment your desires. If you want an Attack Genie, find spells that deal damage. Yes, there are a LOT of spells that deal damage...so look at the spell and see what it does. Maybe it attacks with wood, or fire...figure out what you want to attack with, and how you want to attack. Again, its up to you.
Once you have determined the spells you'll need to fulfill your desired Genie role, note the spells' affinity requirements. Some have none, others have 5 Wood, still others have 1 Metal, 1 Water, 1 Fire...etc etc etc.
Based on the spells' requirements, you'll see how you have to allocate your affinity points.
To review:
1.) Determine what you want your Genie to do for you.
2.) Allocate attribute points accordingly (Str for damage, Dex for accuracy and success rate, Vit for Energy, and Mag for energy recovery and number of spells)
3.) Find spells that compliment your desires
4.) Allocate Affinity Points according to your desired spells' affinity requirements (Wood, Water, Fire, Metal, or Earth)
Again, this is all my take on things. It could be right - it could be very wrong, and I can't guarantee you 100% that this is the way to do things. But the above makes sense to me, and that's how I'm planning on handling this aspect of the game.
And of course...constructive comments are welcome as we all figure out how this whole thing works ^_^
Have fun out there,
-Nurse