Can you use a ability more then once per turn on a card
If there are no restrictions, and you can pay the cost, yes.
For something like {Stonewise Fortifier} where the cost is only a mana cost, you can activate it as many times as you have mana for.
However for something like {Grim Lavamancer} where you have to tap it to activate the ability, you can only use it once per turn unless you can untap the creature somehow.
For something like {Setessan Griffin} you can only activate it once per turn since it specifies that.