Welcome to Goldicq, and this is a topic which main about Atlantica Online foe new players. Hope it can help for you more or less.
In Atlantica Online, You can stop in every town you run across, and enter a town, area or dungeon floor once to get it's map info as well. If you get an NPC telling you to kill mobs on the first floor of a dungeon. Before you go running back to him when its done. Take the time to hit the other area's of that dungeon. That way when he does send you back instead of running you can just teleport to the start of that floor of the dungeon. This is also very important for towns. You'll be covering a lot of ground which depends your level(Atlantica Online Gold) later on.
As tempting as it may be to try to teach your Hero and Merc's every skill available to them. It's not a really good idea for two reasons. The first, In the cast of the Monks protection spell. That is auto cast at the start of your turn. The higher in level it is the more mana it eats. That is to say you'll be sitting a lot or chugging a lot of MP potions. The second, Deluded Characters. You get 1 skill point per level. Teaching and raising skills causes them all to be rather weak. As you are spreading points between skills instead of focusing it into one. So where as my Swordsman lvl 40 Flame Sword is doing 480 dmg. Your Swordsman lvl 28 Flame Sword is doing 200 dmg. Because you dumped the rest of your points into DarkSeed and Guard Dispel. Stay Focused, and plan ahead. The books to remove skills points are expensive(Atlantica Gold), and they only remove one point at time.
You will learn more about monsters Wafter killing them for a long enough time . This is Monster Info and it has 3 stages. Each stage increase the damage you do and decreases the amountof damage the mob does. It also helps in getting better materials and items off mobs. It's random though. Sometimes you'll get all 3 stages fast, other times not so fast. Good thing is you can have someone teach you the parts if they know them.
Thanks for reading.