Smooth Rock - From the route start, head east to find a rail. Grind it and proceed a bit further east to find this.
Heat Rock - Now head just a bit southwest to find a rail. Before grinding it, examine the rock just to the south to find this.
PP Up - Now grind the rail out to a small mesa. Grind the next rail and examine the rock on the next mesa to find this.
Hyper Potion - Use Rock Smash to break the other rock on the same mesa. Slide down the now cleared slope and follow the path. Examine the first rock to find this.
TM47: Charge Beam - Continue along the path until it reaches a short summit. This item awaits you there.
Burn Heal - Grind back to the second mesa and head south. Before hopping the ledge, use Rock Smash to clear the path to your right and reach this.
Sun Stone - Just south of the ledge is a long rail. Grind it to the end to reach a narrow path. Head down the slope to reach this.
Flame Plate - In the southeast corner of the area is a Power Plant entrance. Go there, and you'll spot an item on a ledge just out of reach. Though you can't really see them, there are actually stepping stones between that ledge and the one you're on. Hop across to grab your prize.
Stardust - Once you clear Team Flare out of the power plant, the last leg of the route will be open. Before returning to Lumiose City, head to the right. Use Rock Smash to clear out the short dead end path, then examine the dead end. You'll receive this item for doing so.
Rare Candy - Use Rock Smash to clear the next little bit of the path and grab this.
Zap Plate - After taking out the first Team Flare Grunt, enter the room on the right. This sits in a stall in the eastern corner.
TM34: Flame Charge - Return to this room after kicking Team Flare out of the Kalos Power Plant. Speak to the construction worker near the door to receive this.
Magnet - Speak to the nearby female scientist to receive this as well.
Expert Belt - Head east from the Route 13 exit to find an office building. Ride the elevator to the third floor and speak to the girl near the bookshelf to receive this.
Protein - Speak to the blonde girl next to her to receive this.
TM82: Dragon Tail - West of the Route 13 exit is the Lumiose Museum. Enter and head left. Speak to the purple haired character to receive this.
Bargain Power Lv. 1 - A bit further down the avenue is the Hotel Richissime. Enter to find Mr. Bonding in the lobby. Speak to him for another O-Power.
TM89: Echoed Voice - Head to the fifth floor and enter the room on the right. In the bathroom is a girl facing a toilet (no, seriously). Speak to her to receive this.
Prism Scale - Next to the hotel is another office building. Head to the fourth floor and speak to the little girl in pink to receive this.
Luxury Ball - Head to Autumnal Avenue and enter the store across from Cafe Pokémon-Amie. Tell the girl inside you like "round things," and you'll receive this.
Rare Candy - Just north of the swing set is a narrow path. Head down it to find this.
Tiny Mushroom - You'll battle Pokémon Ranger Melinda just down the route. Next to her is a horizontal branch. Examine the water before it to find this.
Cleanse Tag - Head east and then north to find this in a dead end.
Big Mushroom - You'll spot this when you take the west turn at the fork.
Hyper Potion - A bit further down the trail is water too deep to walk through. Surf across (though you could walk to it using shallow water to the right side) to find this in the water.
TM06: Toxic - Just ahead is a girl staring at a tree stump. Talk to her to receive this.
Damp Rock - Tucked in a corner near the same tree stump.
Roseli Berry - Head east from the staring girl to find the Roseli Berry tree.
TM61: Will-O-Wisp - Just south is a tree blocking the path. Use Cut to clear the way to this item.
Revive - After the cut scene inside the haunted house, head south. Examine the tomb stone on the right side of the deeper water to obtain this.
Spell Tag - Continue south to find this near a ledge.