From a Experianced magicks user
Whenever you get into a fight
determen whether it is worth it to use your spells
If not, save them and let your fighters do the job
If you want to roll play a mage DO NOT take a fighter/mage
It'll make you give him katana's and use him as another tank
Sice you reach such insane levels, Cleric/Mages are a must (to bad you can;t be Druid/mage) or else choose a Sorcerer
Make sure you have a Good thief, this is vital for a mage party as he will have to explore the area and see whether magicks are needed
Make sure you have a "tank" not directly someone who can hit hard but someone who can take a beating, this can be a cleric or a fighter, it'll keep your opponents destracted from the True powers in your party
And for roll-playing aspect it is always better to continue from bg1 to bg2 but in that case you'll have to be a cleric/mage as sorcerers don;t exist in BG1
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Behold he who stands before you
Almighty (shared) Leader of the OHF
Proud member of the Ancients Club
The one True Druidic Sorcerer of the Laughing Hyena's
Last of the Ancient race known as the Red Fluffies
Summoner of Bunnies
Spam Sentinal of the Ironworks
"You can Run, You can Hide,
But you can never do both"
I'm Watching you...