Here are a few sets I quite like, that I've done well with
Set Up Sweeper
252 Sp Atk/4 Sp Def/252 Speed
Dragon Pulse/HP Ice
HP Rock/HP Fire/Giga Drain
Pure offence EV's, enough said.
Bulky Support Contrary
200 HP/36 Sp Atk/252 Spe
HP Fire/HP Rock
EV's are for semi bulk, to take hits better, while racking up Sp Atk boosts. Glare to cripple, and Sub to dodge status. With the above EV's, you can activate the Berry after the third sub, with Stealth Rock damage, or one layer of Spikes, or after the 4th Sub, with less than 1% HP left, with no prior damage. If you wanted a guaranteed Berry Activation on the 3rd Sub, you can play around with the EV's.
248 HP/84 Atk/4 Sp Def/172 Spe
Leftovers/Aguav Berry/Z Stone (Water/Steel/Grass)
Iron Tail/Aqua Tail
Speed EV's allow it to outspeed anything unboosted up to base 102, with Neutral Nature, and base 90 with a beneficial nature. 4 Sp Def because of Download Ability, against this Serp, they'll always get Physical Attack. Porygon and it's evolved forms arent super common, but 4 evs in HP or Def/Sp Def is common, and when a Pokemon has equal base defences, I do 4 Sp Def, just in case. Decent bulk to live medium strength Super Effective hits, and strong neutral ones. Item choice is pretty versatile, and depends largely on what else is on your team. I generally run Battle Bond Greninja, and some sort of Dragon, so I'd opt for Iron Tail over Aqua Tail.