I've never played solo before, but one thing you can do is buy a spell bag, and save every spell you come across. Then, grab any Mage and let them learn all of the spells you may already know for extra XP then remove them from party. You can also grab a Thief, and have them open all of the locks in both Mae'var's guild and Renal Bloodscalp's as well.
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Of course only if you aren't a Thief yourself