Hi!!!! I'm an old player of this game and I've decided to restart it with an Ice Wizard. Do you have any suggestions or guides about which school is best to invest my Training Points? I've heard some things about Death until Feint or Life until Satyr. What do you think?
Depends, for better damage upgrades: Storm, or myth, but its better to go with storm. For a bit healing and a bit damage; Death, better then life. Balance is also good for blades and other stuff. Myth good spend soem but not to much. Some people like spending on life, not me. Fire, idk.
Make sure you also save up training points for when you get to Celestia. Astral spells will be really helpful. Especially Fortify when you first get it (as an ice wizard).
Most people invest their points in other schools for utility spells rather than attacks. Once you reach the mid-to-high levels most equipment you will be using strictly benefits damage spells. Because of this, your attacks will actually end up being more powerful and accurate than if you were to use attacking spells from other schools. Power pips also mean you'll be able to use higher-ranked attacks more frequently.
The general utility spells players go for are: up to Satyr up to Feint up to Tower Shield + Stun Block from Diego (you get these ones for free since you're already )
for the tri-blade and tri-trap from Niles that benefit your school (in your case Elemental Blade and Elemental Trap)
damage spells. Because of this, your 
up to Satyr
up to Feint
for the tri-blade and tri-trap from Niles that benefit your school (in your case Elemental Blade and Elemental Trap)