Wealth
Fire/Poison - Fire/Poison mages have a decent amount of money. It really depends on where you train/the monsters you train on. There isn't really a certain move that can save you money.
Ice/Lightning - Ice/Lightning mages are usually quite poor. Thunder is a skill that uses a lot of MP, so you would need MP potions. Of course, there is always the option of sitting there and resting until your MP goes up, but most players don't do that because that slows down you leveling. However, Cold Beam is quite useful, because you can freeze monsters for a few seconds, giving you an advantage. Some monsters, such as Red Drakes, drop a lot of mesos, so Cold Beam would be useful for attacking them. I/L mages usually train on monsters that have a low MP, so MP eater wouldn't be of much use.
Cleric - Clerics are very rich. They have the ability Heal, which increases the HP of all of the members of the cleric's party. This practically eliminates the need for HP potions. Clerics also have MP eater, lowering their need of MP potions, so using MP eater and Heal, they don't use as many potions as the other classes.
In my opinion, I would think Clerics have the most money in the 2nd job, then Fire/Poison wizards, then Ice/Lightning wizards.
Damage
Fire/Poison - F/P mages do the most damage in the 2nd job.

Fire Arrow has a basic attack of 120 to a single monster when it's maxed, 20 more than I/L's Cold Beam and 40 more than clerics' Holy Arrow.
Ice/Lightning - I/L have a really useful mob attack called Thunder Spear.
Cleric - Cleric's have a mob attack called Holy Arrow. Holy Arrow can only do a lot of damage on undead monsters and devil-based monsters.
In my opinion, Fire/Poison wizards do the most damage in the 2nd job, but Ice/Lightning wizards have the best mob attack in the 2nd job.
Speed of Leveling
This can vary a lot depending on where you train, when new grounds are released, etc.
Fire/Poison - This depends on what you max first. If you max Fire Arrow first, then Poison Breath, you will level at a decent speed.
Ice/Lightning - Ice/Lightning wizards usually level very quickly. Cold Beam is useful when you are at a lower level, so you should max Cold Beam first, then Thunderbolt.
Cleric - Clerics level at a good speed. Since they have the ability Heal, players often choose them to be in their party for CPQs (Carnival Party Quests), which give a lot of experience points.
In my opinion, Ice/Lightning wizards usually level the fastest, then Clerics, then Fire/Poison wizards.
How Interesting It Is
Some people like to play a certain character depending on how fun it is.
Fire/Poison - Fire/Poison wizards have only solo skills, so they rarely ever be in parties. They stay in El Nath for most of the time if they want to level fast. Although, Fire Arrow allows you to go anywhere and still be able to kill monsters quite easily.
Ice/Lightning - Ice/Lightning can mob and have solo skills. Cold Beam allows them to freeze and kill a lot of monsters.
Clerics - Clerics are very good for parties. Even though they do the least damage out of all the classes, they are very helpful to other party members because they have Heal.
In my opinion, Ice/Lightning is the most interesting, then Cleric, and lastly Fire/Poison.
HOPE THIS HELPS!
And this Thunder Bolt, not Thunder Spear (this is third job)