Mag feeding Is quite a complex thing In this game, but I'll try:
http://www.pso-world.com/sections.php?op=viewarticle&artid=1240 Hunter Mag Hunter's Mag Evolution Tree http://www.pso-world.com/sections.php?op=viewarticle&artid=1241 Ranger Mag Ranger's Mag Evolution Tree http://www.pso-world.com/sections.php?op=viewarticle&artid=1238 Force Mag Force's Mag Evolution Tree
Depending on what class you're using, your mag can evolve differently "Once It reaches level 10" on said class.
Then, after reaching level 10, what's next to mag evolution depends on what stat (POW, DEX or MIND. Defense Is Irrelevant, but It's best If you never level It up, for It Is also part of the Mag leveling), your mag evolves according to each trees. It means, for example, If your mag's POW Is superior than DEX & MIND, then It will evolve Into the POW mag (according to the tree), and so goes for the same with DEX & MIND.
(Like said before, Defense doesn't have much of a role, unless you are going for the Special Mags, but that's another thing mentioning later) *Important to know: If your mag evolved according to any of the classes for the first time, Its second evolution will keep evolving to said class evolution, too, no matter what other class you are using.
And then, for the third evolution, the conditions thickens a little. Now, the conditions for your mag to evolves depends on a "Stat < Stat < Stat" pattern. Like POW < MIND < DEX, or POW < DEX < MIND, and so on.
Know that It doesn't matter If your second evolution was based on POW, DEX or MIND. If you can manage to raise a stat above the superior stat on the second evolution, you can change the direction of the evolution tree. Like, your second evolution was based on POW as the superior stat. If before reaching level 50, you manage to raise another stat, be It DEX or MIND, your mag can evolve with a new pattern.
*Another Important Info to know related to the previous "Important to know": Do you remember how a mag's second evolution Is related to the first evolution, that It depends on what class evolve It? Well, on third evolution, It doesn't matter what class evolved your mag for the first time: A mag's third evolution depends on what class evolves It for the third time, plus.... Its evolution also depends on a character's ID. (Yes, Purplenum, Pinkal, Redria, Whitil, all of those IDs. Of course, according to each class mag evolution, there are only two columns with spread IDs, so there's only two sections on how IDs can make a difference on Mag evolution, too)
The three class' mag evolution tree shows In detail how they evolve
http://www.pso-world.com/sections.php?op=viewarticle&artid=1021 Mag Charts Mag Feeding Chart
This chart shows how much each Items feed the mag's stats. Somewhere here In the forum there Is a strategy on how to feed them, so one doesn't have to worry too much on order and such... (and I can't find It at this moment )
http://www.pso-world.com/sections.php?op=viewarticle&artid=2343 Episode 4 Mag Evolution Guide
The name says It. Everything you want to know about them Is there.
http://www.pso-world.com/sections.php?op=viewarticle&artid=1031 Special Mags guide.
In order to create these mags, certain conditions must be met. You can see more In there.