You know how in Diablo 2 you get 1 skill to put into a certain tree and you can spread it out, if you so choose?
Well on the server you will obtain X amount of Spell Credits when you level (Undecided how much), and you will be able to essentially PUT those spell credits to obtain that spell. This will prevent people have Ice Bolt I - III and Inferno I - III along with Thunder Storm I - III.
VVV THIS IS ONLY AN EXAMPLE AND MAY NOT BE APART OF THE SERVER VVV
Lets say for instance here;
$spellrankI costs 5 Points
$spellrankII costs 10 Points
$spellrankIII costs 15 Points
You get 10 points per level, you can 'buy' $spellrankI ICE and $spellrankI FIRE and then be out of points, when you level again, you can either buy $spellrankI MAGIC or buy $spellrankII ICE//FIRE.
To make it as clear as possible, here is a picture;
The name is blanked out because it's not a 'child' appropriate word to post on the forums. :P
^^^ THIS IS ONLY AN EXAMPLE AND MAY NOT BE APART OF THE SERVER ^^^