I wouldn't put Substitute actually
My set would be:
Serperior @Lum Berry
252 SpA / 4 HP / 252 Spe
Knock off is really useful against tanks that it can't OHKO
Synthesis is for healing because Serperior has decent bulk and can withstand a few hits
Lum Berry is for Hypnosis or Thunder Wave. Paralysis would DESTROY Serperior because it would be too slow and there's a 50% chance it can't even attack.
Dragon Pulse is there because it's a good special move and it's for coverage
Leaf Storm is obvious; it'll give Serperior a 2x SpA boost due to Contrary
Even though it can learn coil, Contrary gives it a free boost, while u need to use a turn for coil.
So, overall, Contrary Serperior is worth it.