Will i be able to use more than one spell with mage? I want to play with mage party and i do not know if have to put water and air to one mage or water to one and air to second. Because of possible combination. I can use only spell per turn now, so it is better to have water on one and air on second. Bud later if i will be able to use more. It is better to have it on one mage.
Intelligence do not increase AP by the description in game so i need to put some points to speed. But if spell use like 6AP i need to put a lot of points to speed...
Any character can learn any number and combination of skills/spell schools. So yes, you can have both aero and hydro on the same mage.
As for AP, don't waste all your attribute points on Speed. Yes, it's definitely worth investing in, it's probably the most useful stat for most next to their primary stat depending on skills. But you will find a lot of gear that lets you increase the number of AP in one way or another, and the spell Wildfire will give you a good boost. The Glass Cannon talent is extremely useful on a caster and will let them cast several spells every turn. Also, don't be afraid to save AP from one turn to the next to be able to cast more expensive spells.