Try this set. I'm thinking it will work well. My Serperior has a set very close to this one.
Items: Light Clay/Big Root
Light Screen- For dual-screening. Surpresses special attacks.
Reflect- As mentioned above. Surpresses physical attacks
Leech Seed- Steals your opponents HP and replaces your with some. Works well with the big root.
Toxic/Giga Drain/Leaf Blade- For this one you can pick which one suits your Serperior the most. If it's attack stat is higher than special attack, go with Leaf Blade. If not, just go with
Giga Drain. Toxic is just a great move to work with Leech Seed, but I wouldn't suggest using it with all the Taunt users nowadays. Oh yeah I forgot, if you go with Leaf Blade or Toxic, don't use the Big Root because you won't be using it to it's full advantage. Use it if you are using Giga Drain.
Here's a physical set.
Leaf Blade- Overall great move. This is a must.
Dragon Tail- If you don't like your foe, switch them out. Works well with a teammate with moves of spikes, toxic spikes, and stealth rock, so basically a fortress. Sorry I couldn't think of the name. Also good base power for this type of move
Swords Dance- Yeah this move should have been listed first, but it slipped my mind. It's another must for any physical sweeper.
Iron Tail/Aerial Ace/Taunt/Synthesis- If you really want an all physical attack set, don't use Taunt or Synthesis, Though out of these four, I would go with Synthesis, well because grass types have many weaknesses, specifically, five. Iron Tail and Aerial Ace are for coverage and Taunt is for all those walls with only status moves. Yeah it makes me laugh when I make walls struggle to the death.
Next, I could list a Contrary set, but it's pretty obvious that Leaf Storm is a must, and the rest are basically fillers. Well then, yep! That's it. Until next time, see ya!