Hrafnagudh: Hello everyone!
I just began MoM, already loving it.
I have a pair of questions:
I see TwoHandedSword has already given basic answers to your questions. I'm here to talk your ear off with details and extra data. ;)
First thing to know: are you using the basic GOG install? There is an Insecticide mod/patch (there is a stickied thread with information) that a number of people use. There is also a Help file replacement around somewhere, which replaces nearly all of the text that you can see by right clicking on stuff. I use the basic GOG install, and my answers will be in line with that.
Hrafnagudh: 1) I summoned Sprites for explore and kill small groups of enemies. In battle they have 4 ranged shots and then only melee. Well, after I used all the shots I start moving the Sprites around, but they are like having unlimited moves, with the enemy doing nothing. Can you explain what is happening?
The AI won't move its units if there is nothing for them to do. Your sprites fly, and most units can't initiate an attack on flying units (the attacker needs to be able to fly, or have certain abilities (examples include "Thrown", "Fire breath", and "Stone Gaze"). The computer won't bother chasing the sprites around the field if the unit doing the chasing can't do anything even if it catches up. If the unit has ranged attacks, it will shoot at you, but it won't give chase after running out. Most Barbarian units would happily chase the sprites, since most of their units have a Thrown attack which will allow them to initiate an attack on the flying sprites (assuming they could catch up to the sprites).
THS mentioned the 50 turn time limit. After 50 turns (both attacker and defender get 50 turns each, with Defender going first), the battle will automatically end and all attackers will retreat. Normally, retreating will cause the game to roll dice to see if any retreating units are lost during the retreat, but those dice are NOT rolled when the 50 turn limit is hit. Also, the battle will count as a victory for the defender, so any dead defending units with regeneration will return to life, etc.
Note that if you are defending a city with a flying unit, if enemy units can get into your city, they WILL start walking around in it even if they can't touch your flier (especially if they can't touch your flier). Any time an attacking unit walks on a "city tile" during combat, there is a chance the city takes some 'extra' damage (maybe more buildings will be lost, or more population killed). So a single unit of sprites can keep an army of walking paladins from actually conquering an unwalled city, but the paladins are going to try and wreck the city before the battle ends. If the sprites are blocking the city gate, then the paladins won't bother moving (because they can't get in the city).
Hrafnagudh: 2) On the magic menu, the Casting Skill Ratio is useful just for improve the casting skill number below? If yes, when should I put some points there, when I need to cast spells with more mana?
Yes, the Skill slider is for increasing your casting skill. As THS said, your casting skill is slow to increase (it takes roughly 2x+1 power points to increase your casting skill by one point, where "x = current casting skill"). The Archmage retort will multiply the amount of power you spend on increasing your casting skill, otherwise it just depends solely on how much power you've been putting into it. Start early, and put in as much as you can spare.
Your casting skill determines both how much casting you can do in any given combat, and it also determines how much mana you can channel into casting spells each turn on the overland map. Any given combat gets a full allotment of your casting skill (regardless of number of combats in a turn), and none of those combats affect the amount of casting skill you have available for casting overland.
Mana crystals can be found in lairs, nodes, or enemy wizard towers. Alchemy (the ability on the Magic screen, not the retort) can be used to convert gold into mana, or vice versa (one of the things the Alchemy retort does is make the conversion a 1:1 ratio)
Spells can be found in lairs, nodes, or enemy wizard towers. Spell research points can be provided by certain city buildings or hero abilities.
Spell skill is all about how much power you spend on that slider each turn.
Hrafnagudh: 3) Speaking of magic menu's staffs, how do I increase the magic power?
A number of things give power points. Religious buildings (like the Shrine) give power. Certain magical races give power per population (high elves give 1/2 power point per high elf citizen in your empire). Nodes provide power to you if you have a magic/guardian spirit melded with the node. Any volcanoes that you created (chaos magic) will provide one point of power each.
Certain retorts will multiple certain sources of magic power. For example, Node Mastery will multiple the power you receive from nodes you control.