Lone wolf with nearly any build will be successful. Going solo as a magic fighter you'll need to spread your points out between all the different magic types or else you may encounter a fight where they're immune to your specialty. Dual wands is probably where you want to live unless you need some damage mitigation, then go wand and shield. Going solo you won't be able to use the Stench skill because you're the only game in town, so everyone will attack you. Summoner is super OP once you get to level 10 summoning; that incarnate hits like a truck and you can infuse it with whatever element the enemy is weak against. Whatever you pick, make sure you give yourself tons of mobility, stealth, and crowd control skills.
