Battle Moveset

A Good Moveset for Spoink would have to be this:

Attacks:

Light Screen
Reflect
Psychic
Toxic

Items Attached:

Leftovers

Preferred Nature:

Timid

Strategy Using Spoink

Introducing Spoink, the pig on the spring and a quite unique pokemon.
This pokemon has quite poor defense and attack, however this doesn't make it a bad pokemon. It does have slightly below average special stats. Its speed isn't too bad either.
This moveset is simple, set up a Light screen/reflect and switch to a different pokemon. If you don't want to leave it here, use toxic(or replace with confuse ray to add that extra chance of your opponent missing.) and then reflect/light screen and switch.
Leave the trickbanding to the evolution and just use Spoink as a supporter. Use Psychic incase this pokemon is your last, it may come in useful when you need it.
Put EV's into Speed and Special defense, putting any in defense would be a waste since a majority of physical attacks could knock out Spoink in one hit, even if it was boosted with EV's.
Overall, Spoink isn't such a bad pokemon and when it evolves it is most likely one of the better psychic pokemon available.

EV Corner:

Max out the EVs in Speed & Special Defense for Spoink with any remaining in HP

Strategy Against Spoink

Spoink's Physical Defense is weaker than it's Special so either go with Super effective like Dark or Phyiscal attacks and it'll be down in no time

Contest Moveset

A good Contest Moveset for Spoink would have to be this for the Smart Contest best with Calm, Gentle, Careful, Sassy Nature:

Attacks:

Calm Mind
Psychic
Shadow Ball
Confuse Ray

Items Attached:

Green Scarf

Strategy Using Spoink

If you do the attacks in this following order you should have very few problems; 1st - Calm mind, 2nd - Psychic, 3rd - Calm mind, 4th - Psychic/Shadow ball, 5th - Confuse ray

Locations in Games

Ruby/Sapphire Route 112 Colosseum Trade from R/S Fire Red/Leaf Green Trade from R/S

Animé Appearences

Spoink has had one Animé Appearence. In it, it had lost it's ball which is the source of it's power. Ash & Co. have to help fine it Episode 355: Spoink's Lost Object!