The previous guide was taken out because the owner of the guide QQ'd way too hard. So I made my own based on my experience in Pockie Ninja.
Make sure not to use any coupons unless the quest requires it. Only use coupons for skill resets if you reach level 25 and still don't have the right skill build for you. Other than that just save up your coupons till you're around 31. At that level you can really use the coupons to buy Exp Seals(Or you could just synthesize them) and they could also be used to upgrade your equips.
Leveling from 1-16
Starting from the tutorials, tutorial quests, and main quests getting to 16 should be easy in your first 2 hours of play. 15-16 Will take the longest since by this time(if you're not using any exp seals from the newbie gift pack) you're going to need to keep on attacking the highest level monster you can to level up.
Leveling from 16-31
From 16-31 it's going to take maybe 3 hours of leveling. Finish up all the quests you get after each level up and proceed to killing the highest level monster you can kill(except for maybe the Las Noches Quest and the Valhalla Hard Quest). Always go for the Demon Elimination Bounty Quests to help you out.
Leveling from 31-onwards
At this point you notice that leveling gets slower and slower. You can barely make 1-2 levels in a day. Always complete the Demon Elimination Bounty Quests to help you out. Always finish up all the quests you get after every level up. This is when you use your Exp seals and your coupons to help you level up. Buy exp seals when you're going to go grinding for experience. The best place to go after finishing up quests is 31 Slots at Dawning Wilds. It gives decent exp and you have a chance to get unbound items you can use to sell and help you get better equips.
Misc. Places to get Experience
This place is more of an Equipment and Stone farming place but be sure to use up your 3 tries everyday because the equipment and stones you get from here will help you level up in the future.
Save this place for last after you finish up with everything that requires movement and do this before going to Arena. This is a great place to get exp. Though it does get boring after a while.
If you are a master you get exp after your apprentice finishes it's time with you. If you're an apprentice you get exp every time your master gives you a present.
You can trade your medals for experience in the Arena but I strongly advise against this since you'll be needing your medals to open jars for free suits you can use to upgrade your main suit.
At lower levels your options are limited on how you obtain stones.
Your only options from 1-30 are (besides opening jars bought with gold):
From 31 onwards you're going to be earning alot from slots. Since there is a chance to get unbound 2s, 3s, and 4s items. You can sell them at the trade market and make big profits. I personally make around 200k a day.