At level 26 fireball is more cost effective than shockwave. Fireball costs 18, shockwave costs 33. And it's important to conserve mana until you receive kickback from the kill.
The most powerful spell in terms of damage is malediction, though it costs half your mana to use.
Most of the times I just kill things with acid danmaku though :V.
Also, remember to increase both wisdom and constitution to 18 before you level. Also remember to max out intelligence to 18 before attempting to practice any skills/spells.
I'll be collecting items that boost these so "link" me whenever I'm on if you need it.
You can also collect items yourself, here's a quick list of what mobs in Medievia City drop what items:
Traveler
Appears as: A journeyman hops excitedly down the road, talking to those nearby.
Drops: A bracelet of interwoven leaves, randomly gives 0-2 Wis and 0-2 Con depending on your luck.
Found: Head east between recall and the gate to exit medievia, they spawn randomly there.
Clerical Scholar:
Appears as: A tall man in a black robe and mortarboard walks along, his nose in a book.
Drops: WIS 1-3 CON 1-3 a scholarly tome
MANA 10 WIS 2 a black scholar's robe
MANA 10 INT 2 a black mortarboard
Found: Randomly around the cleric quarter of medievia. "Enter cleric" at recall and wander around.
Mercenary:
Appears as: A heavily armored mercenary is standing here, looking for work.
Drops: An Oaken Scabbard 2Str 2Con
Found: Throughout the city, but can be easily found by heading south of recall.
Ragamuffin:
Appears as: A cute, dirty ragamuffin is standing here, smiling at you expectantly.
Drops: [HP 7 CON 2 ]a staff of knowledge..humming quietly
[INT 3 WIS 2 ]a woolen hat, woven into the shape of a cobweb
[HP 10 CON 1 ]a floral dress of wool
(Stats may be different)
Found: In the thief quarter of medievia.
Don't attack the guardsmen, they'll mess you up easily.
Golden seal potions are available in a shop 3E 2N of recall, quaffing them heals you so stock up as necessary. They're a steal at 55 gold each.