Boost your critical strike. It's so worth it. Buy a Jade Ring (assuming a slayed slime or fishing chest haven't already given you one or three) and, if you can, the Steel Falchion or Lava Katana (Neptune's Glave is also good, but I think you can only find it in fishing chests). When your Combat skill gets to level 5, choose 'Scout', then at level 10, choose 'Desperado'. I one-shot so many serpents (and bats, slimes, rock crabs, ghosts...) this way. Later on, I boost the crit chance and damage on the Galaxy Sword when I can and add the 'Crusader' enchantment. Then I can take out Mummies in 1-3 hits, too.
For food, I usually just use the free veg of the season for the first few years and then stick with Summer Squash or Broccoli as my main. If you have the Vampire ring and you're killing enemies left and right, then you'll rarely get low enough to worry about big boosts. If you are getting beat up though, either plant plenty of tomatoes & eggplant or build a fish pond and throw in some crabs. Crab Cakes (+1 defense & speed) and Eggplant Parmesian (+3 defense +1 mining) are good for SC runs. You can also eat the Spicy Eel that the serpents drop (they sometimes drop Crab Cakes, too) for a speed & luck boost.