This set has probably been posted here 10 times...
Ditto@Choice Scarf/Leftovers/Choice Band/Choice Specs/Focus Sash
Do I need to explain this set? The item choice is for what you want. Choice Scarf allows it to strike first against opponents. Leftovers allow it to recover if it transform against a wall. Choice Band and Specs can be used if it transform into a Physical attacker and Special Attacker respectively. Focus Sash allows it to live longer.
Next Week: I would say Celebi but no legends so...Sceptile.