Level 1 - 150
First thing to do Use the 2 Potions of Experience then go kill any 150 mobs you find, to reach level 150.
Now you can wear all the Devil gears once you add your stats points accordingly. Epaulet requires level 165.
Go to higher level maps, Senillinea/Chrysos/Nostalgia or medium/high level dungeons for the rest of the levels.
Do not expect to be able to kill the bosses if you choose high level dungeons, stick to mobs around.
Once you reach level 200 its time to get better gears.
From here on its all about your choice and your play style.
Farm low/medium dungeons or go for the higher maps to achieve Absolute and ultimately Paladin Gears.
Runes drop in Steamer Crazy and Forbidden Island.
When you feel geared enough go for the High Dungeons.
Check the Drop tables for full info about the gears drops.