All spells have a Rune Cost. To keep things simple, the Rune Cost will not differentiate between different types of runes. Instead, all runes are counted as one number and the spells draw from that number.
Note that these costs are cumulative, not additive. Casting a T5 spell costs 10 runes, not 30.
Runes are common since Runecrafting was rediscovered in the late 5th Age. However, being in Morytania makes even the most common supplies harder to come by. You can replenish your rune supplies by heading to a town and spending gold.