. . . Water expert and master as soon as you can. The huge disadvantage of expert is that you can only cast the Town Portal and Lloyd's Beacon spells when hostiles are well out of range. Outside, you stand an excellent chance of being able to run away if the situation goes bad. Indoors, there are some instances when you will get trapped, notably when you open the door to the dwarves' main hall in Snergle's Caverns. You'll have a mass of dwarves in from of you, and probably about 10–12 more will materialise behind you, blocking your retreat. You will need either to be fairly hard to win the battle, or to be able to bug out to a prearranged LB position back down the passage.
I have minimal experience running solos characters, but one of my tips would be to do as much fighting as you can at long range, and to get your resistances up as far and as quickly as you can. So get your magic and Bow skills up, and get the best bow you can find. There are a number of monsters that can take out a character in an instant attack, (e.g. one of the Werewolves, the Medusas, the Supreme Titan, one of the Beholders, Agar's menagerie, and others) and with a solo character, if something as simple as a Sleep spell gets through your defences, then it's "Game Over".