The thing about the Nemesis fights is that they require a specific class-tuned strategy. For Saucerors, Lumpy (your Nemesis) has a special attack that he'll unleash every now and then. If you don't have a Saucesphere to protect you, it will OHKO you. But if you do have a Saucesphere, Lumpy will absorb the sphere and then hit you with more damage on the second round.
Taking this in mind, the most important stats to worry about are Mysticality and HP. With Lumpy's massive 500 HP stat, you aren't going to take him down unless you have enough Mysticality to cast 100+ damage Saucemageddons. You'll need to maximize your HP as well as you can so you can survive long enough to cast 5 Saucemageddons.
You can look here to find some tips on increasing your HP efficiently. However, most of your bonus HP will probably come from effects as most of the best equipment for bonus HP isn't wearable until aftercore.
Don't forget that HP also scales with Muscle. Grab Muscle-boosting equipment and effects like Ferrigno's Elixir of Power to boost your Muscle. And since you're a Mysticality class, use an oil of expertise (cherry cooked with scrumptious reagent) to boost Muscle and Moxie to equal your unbuffed Mysticality.
Lumpy is a simple tank-and-cast fight, so once you have enough Muscle/HP to survive his onslaught, it should be matter of just clicking through.