I didn't make this guide from scratch, I referred to the old guides, thought it may be useful for new people here. Hopefully the farming tips below are still relevant in here.
Tips 101: Always try to sell the loots with your character that has level 10 overcharge so you get more zeny!
Either target only Mavkas or also Baba Yagas for optional loots. You can get around 3-5 million zeny in 30 minutes!! And lastly dont forget to use these @alootid commands unless you want to be a Kukre and loot everything, which is never a bad idea!
Witherless Rose: @alootid +748
Crystal Mirror: @alootid +747
Piece of Cake: @alootid +539
Blue Herb: @alootid +510
Prices (without Overcharge skill)
Witherless Rose: 27,500 zeny
Crystal Mirror: 7,500 zeny
Piece of Cake: 1,500 zeny
Blue Herb: 30 zeny. This is better off stored or sold to Blue Pot Crafters or other players with higher price. Players also need blue pots, if necessary, store it.
Ein Dungeon Level 2
The main item you want to get here is the "1carat Diamond" that the Obsidian monster carries. They drop it all the time (if not, then most of the time). The Teddy Bear drops "Oridecon Hammer" and the Mineral drops "Topaz" (and in rare occasions, "Gold"). Here's list of how much they sell: 1carat Diamond = 5000z
Oridecon Hammer = 2500z
Topaz = 3000z
Gold = 100000z (you can vend this to sell to players for higher value, since gold is useful i.e. for handcrafting)
Geffenia (level 4?)
Monsters : Succubus, Incubus, Mini Demon with 2 spawns of Deviruchis, Violy, etc. etc.
Little Evil Wing = 1000z
Mastela = 4250z
Gold Ring = 15000z
Diamond Ring = 22500z
For the Priest class: use Magnus Exorcimus skill (with No Cast-Time) except for Fake Angel and Violy.
Abysmal Knights do roam around these areas every now and then. If you happen to kill them, there's a little chance they might drop an Abysmal Knight Card, which can be sold to players for quite a price.
Sphinx level 4 / 5
Monster to kill: Pasana. Main items to loot: "
Undershirt" and "Stiletto" (bear in mind the drop rate is not 100%). This monster is mostly around and can be spotted easily. Level 5 has more Pasana spawns than level 4, though in level 5, there's Pharaoh MVP, so make sure you choose carefully! Undershirt = 10000z
Stiletto = 9750z
Juperos (core/ruins 1) Monsters: Venatu and Dimik. They are aggressive and can gang up on you very easily so stay alert.
Crest Piece (any kind) = 2500z
Professional Cooking Kit = 1000z
Drifter = 40000z
Dusk = 11750z
Thunder-P = 38000z
Armor Charm = 10000z
Steel = 7500 (can be sold to players for better price?)
Tips: A Wizard / High Wizard with No-Cast of AOE (Area of Effect) like Storm Gust and Lord of Vermillion skills can pretty much swipe clean the area. Assassin / Assassin Cross types can also round up as many as they want (just make sure you have enough Flee rate to dodge their attacks) and once they have formed a line trying to attack you, use Hiding and Grimtooth (must have Katar type weapon to be used).
I'll update this when I have more time. Let me know if you have any feedback so I can also update this post. Also let me know what guides you want to see.
I don't take any credit for this guide.