This deck uses Claydol and Grumpig, an unlikely but synergistic pairing on closer inspection. Both are solid attackers, Claydol being able to Confuse, and Grumpig having Ludicolo's iconic Circular Steps attack for big damage. Backing them up are a host of tech Basics.
Lead with Baltoy, evolve to Claydol, and use Psychic Trace to set up. Fill your Bench with the tech Basics if they will have a disruptive effect on your opponent, or more Baltoys and Spoinks as future attackers. Grumpig's damage grows the more Pokémon are in play.
You can attack with either Claydol or Grumpig. Claydol's damage is lower, but it Confuses, and if it's in the Active Spot, it can use its Poké-Power to keep the cards flowing while you're getting aggressive. If the opposing Pokémon will take two attacks to KO, you'll want to try and attack with Claydol first to chip and Confuse them, before finishing them off with Grumpig.
This deck doesn't have many more tricks with regard to attacking. It's usually just "build up more Pokémon on your Bench and send them in after the Active is KOed". Sometimes you can fish for status with Psyshock or Disorder, or a lucky Hyper Beam flip discarding an Energy card that provides 2+.
This deck sets up with Claydol, which is rare — the usual suspects are Jirachi and Pidgeot. However, those two aren't as good at attacking as Claydol, who does 40 damage (30 if using Double Rainbow) plus Confusion for 2 Energy.
Despite being a 2-color deck, the Energy is fairly smooth. Double Rainbow Energy or Holon's Magneton will provide both colors for Claydol's Ancient Mantra, as will Multi Energy plus any basic. Double Rainbow or Holon's Magneton plus Multi still pays for Grumpig's Circular Steps, even though Multi only counts as Colorless in that case.
Switch/free retreat cards (Warp Point, Fluffy Berry, Mr. Briney's Compassion) can let you get multiple Psychic Traces in one turn without wasting Energy on retreats, provided you have more than one Claydol.
Alakazam ☆ can Skill Copy Holon's Magneton's Extra Ball to do 100 damage to Psychic-weak ex's. However, you will need Multi Energy to do this, since it can't have Double Rainbow Energy attached.
Dodrio: Reduces the Retreat Cost for everything except Mr. Mime ex to 0. However, if it gets dragged into the Active Spot, it doesn't get the Retreat reduction.
Claydol and Grumpig cover each other's weaknesses extremely well. Claydol is weak to Water, which Grumpig can sponge with Thick Fat, and hit several common Water-types back for Weakness (Mew ☆ δ, Latios ex δ). Grumpig might get walled by Darkness-types that resist it (Dark Tyranitar, Rocket's Sneasel ex), but Claydol hits those for Weakness.
Grumpig's damage potential is very high. With both Benches full, Circular Steps does 100 damage after Double Rainbow Energy's debuff. This is conditional on having full Benches, but if you look around, usually only Stage 2 ex's get 80 damage for 3 Energy, so Circular Steps is still above rate. Grumpig is a one-Prizer, Stage 1 (fewer cards to set up), and gets to use Double Rainbow Energy to speed things up.
Spoink and Grumpig have traits that serendipitously improve certain matchups. Spoink has Psywave to counter Scrambled Eggs, and Grumpig has two pseudo-Resistances (which work even when it's Benched, unlike actual Resistance). Arcanine ex is hard walled by Grumpig; it can't turn off Thick Fat, can't do any damage with Overrun, and Flame Swirl leaves Grumpig with 10 HP after Thick Fat's reduction.
Grumpig relies on having more Pokémon in play to do damage, so Giant Stump can throw a wrench in that plan. If you need to keep Lunatone and Solrock around post-Stump, that leaves only 1 free space on the Bench.
Both of the main attackers are weak to Banette ex. It resists Claydol and 1HKOs Grumpig with only 2 Supporters in the discard. This is what Mr. Mime ex is primarily for, as once they hit max Supporters in the discard, Shadow Chant is the right parity for Magic Odds to negate. You can do some damage against Banette with Claydol if Magnetic Storm is in play.