Here  is how to change the number of spells coins and weapons you
have by editing the save game:

OFFSET          NEW VALUE       DESCRIPTION
05D             00-FF           Invisible
078             00-FF           Gold Coins
08C             00-FF           Sulphur
092             00-FF           Venom clouds
098             00-FF           Fireball
09E             00-FF           Lightning
0A4             00-FF           Reveal
0AA             00-FF           Heal
0B0             00-FF           Teleport
0B7             00-FF           Levitate
0BC             00-FF           Bombs
0BF             00-FF           Monsters