Yeah, Larka sent me a PM that explained things better. Here's my revised F/P build INCOMING WALL OF TEXT:
1st job
1 Energy Bolt
Max Magic Claw
Max Magic Armor
Max Magic Guard
Max MP Boost
7 (+6) Energy Bolt
Spoiler
This build should be standard for all adventurer magicians. 1 Energy Bolt is required to unlock Magic Claw, which is your main attack skill for 1st job. Magic Armor is taken next. It reduces the amount of damage you'll be taking in 1st job by about 30. Nothing in 1st job does enough damage to really warrant getting Guard first. Guard is taken next of course, to increase survivability. MP Boost is taken last since you have more MP than you'll know what to do with anyway. Spare points go into Energy Bolt, though you will never ever use it.
2nd job
1 Fire Arrow, 1 Teleport
Max Spell Mastery
Max Fire Arrow
Choice -
1. Max (+19) Teleport, 3 MP Eater, Max Meditation or
2. 3 MP Eater, Max Meditation, Max (+19) Teleport
Max (+17) MP Eater
Max Slow
1 Poison Breath
Spoiler
Take 1 Fire Arrow at level 30. It has significantly more range than Claw and hits an additional target, though you'll still be using Claw on single and double targets. 1 Teleport is next because of the incredible mobility it provides. Mastery isn't as important for mobbing classes, in my opinion, because average damage matters more than stability, but it is still the best source of damage, so I would take Spell Mastery next. Fire Arrow should be maxed afterward.
Here we come to a part where others might disagree with me. I have always been an advocate of maxing Teleport as early as reasonably possible. Maxed Teleport lets you move faster and spend less time mashing your MP potion button. I use Teleport extremely often and on low level mages I always need to pack a lot of Sorcerer Elixirs. Meditation is another good option, but 1. you can always use potions to take care of that damage boost, and 2. the monsters are so weak that even a completely unfunded character will be clearing out the spawn faster than they can reach it. I'm leaving that open.
MP Eater doesn't steal the thousands of MP that it does at higher levels in 2nd job, so it isn't as good as maxing Teleport and gets maxed afterward. Slow is maxed last because it is only useful for bossing and doesn't really benefit you in 2nd job.
3rd job
1 Teleport Mastery, 1 Explosion
3 Elemental Amplification
6 Spell Booster
Max (+17) Elemental Amplification
Max (+9) Teleport Mastery
Max (+19) Explosion
Max Poison Mist
Max Elemental Composition
Max (+14) Spell Booster
Max Elemental Decrease
Max Partial Resistance
11 Seal
Spoiler
Take 1 Teleport Mastery at level 70. This is an INCREDIBLE skill and easily my favorite skill in the entire game. It lets you move faster and if used properly, it is basically a free mob attack that can be activated between skills. In my opinion, any build that does not get Teleport Mastery immediately is just plain wrong. 1 Explosion is useful because of the large range. Explosion scales poorly and does 80% of its max damage at level 1, so it can be delayed for the moment. Amplification and Spell Booster are taken next, because they are huge boosts to your overall damage.
I find both of the 3rd job mobbing skills underwhelming. Poison Mist is good on paper, but all the mobs you'll be training on are too weak for you to really take advantage of it. Nothing takes 2400% damage to kill, and you will only be wasting your time casting it. Explosion is too slow and you can't spam Teleport in between casts, which really hinders it. Its primary advantage over Fire Arrow is simply its huge range. It can be useful for training at Galloperas (even if they are fixed) and Captain/Krus, but both of those are higher level mobs, so it does not need to be maxed very early. So instead of getting either skill, I would max Teleport Mastery first. It actually scales quite well and you will be using it very often. Explosion is taken next, followed by Poison Mist.
The rest of this build is just filler. None of these skills are useful to your training at all, but they can help you with bossing and maybe other possible applications down the road. Composition is a decent 1v1 attack to have, so I'd max that first. Booster's timer is a bit short at 60 seconds, so I'd finish that off next. Everything else can be taken in any order. Seal is left at level 11 because it is completely useless.
4th job
1 Paralyze, 1 Meteor, 1 Big Bang
Max Buff Mastery
Max Paralyze
Spoiler
The top three lines of this build are the no-brainers that I've posted before. Each of these skills is useful with just 1 point in them and this build starts you off with a good arsenal to work with. Buff Mastery is next because the damage increase is unbeatable without nearly 500 Magic Attack, and soon you will have 7/8 (counting Decrease) buffs to cast, which is extremely hard to manage without nice 5+ minute timers for everything. Paralyze is next because it will be your primary attack skill in 4th job.
Since 4th job is mastery book-based and pretty open-ended, I will just give a quick summary of each skill instead of a specific build to use.
Big Bang: Low-Medium priority skill. Big Bang is a good skill, but your primary use for it is to charge it up while dropping down a platform or before climbing up a rope in order to immediately take out a mob. Its range is crap compared to Explosion and it's usually easier to spam Paralyze to take out mobs because if you release it while getting bumped, you lose your charge. Big Bang scales extremely poorly and deals 80% of its max damage at level 1. It also usually 1hkos mobs with decent funding, so there's not much of a point in adding more points. May be more useful at Lionheart Castle.
Infinity: Medium-High priority skill. Infinity is an good damage boost and can speed up training a little bit. It scales in a way that makes it almost useless at lower levels, so it is an all-or-nothing skill. Don't leave it at 10 or 20, max it if you plan on getting it.
Meteor: Medium priority skill. Many people assume that ultimates are useless now that they have a cooldown. This is completely false. Meteor is stronger than ever and like Big Bang, it is pretty much a guaranteed 1hko. Large maps can take over 30 seconds to cycle, and a well-placed Meteor can save you a bit of walking. Paladins think Heaven's Hammer is great, and their ultimate doesn't even kill mobs. The 30 second cooldown on Meteor does make it a bit less useful than Air Strike and Dark Fog, but it can still help your training. Meteor can even boost your bossing damage slightly, thanks to the DoT.
Maple Warrior: Medium-High priority skill. Maple Warrior is a solid damage increase and can help an entire party, although as a common skill it is pretty much guaranteed that someone will have it if you don't when party training/bossing.
Ifrit: Low-Medium priority skill. Ifrit is an acceptable boost to your overall damage and is useful for clearing mobs without physically having to attack them.
Fire Demon: Low priority skill. This skill is pretty much useless for the moment. Its damage is pitiful, even weaker than Fire Arrow, and the elemental shift doesn't do you too much good since you have Elemental Decrease now and as stated before, Big Bang 1hkos things anyway. It does boost your bossing damage slightly thanks to the DoT.
Hero's Will: Low priority skill. It's very situational.
Mana Reflection: Rejected skill. Leave this unmaxed if you get to 200.