All Mega Stones order

Set clock so High Tide/Low Tide

Do Any%/E4R2 (but stop after Deoxys)

1 Alakazite (Slateport)
2 Latiosite (Southern Island)
3 Swampertite (Route 120 from Steven)
4 Medichamite (Mt. Pyre Top Floor)
5 Banettite (Mt. Pyre Summit)
Do Shoal Cave high tide
6 Sablenite (Sootopolis)
7 Heracronite (Route 127)
8 Mewtwonite Y (Pokemon League)
Any% done

9 Mewtwonite X (Littleroot Town)
10 Aggronite (Rusturf Tunnel)
11 Mawilite (Route 117)
12 Gardevoirite (Verdanturf Town)
Get Intriguing Stone in Verdanturf as well
13 Steelixite (Granite Cave)
14 Beedrillnite (Sea Mauville)
15 Aerodactylite (Meteor Falls)
16 Pidgeonite (Rustboro City)
17 Scizorite (Petalburg Woods)
18 Gyaradosite (Route 123)
19 Abomasite (Route 123)

Catch Swablu

20 Altarianite (Lilycove City)
21 Cameruptite (Team Magma Hideout)
22 Pinsirite (Route 124)
23 Glalieite (Shoal Cave)
24 Slowbronite (Shoal Cave)
25 Kangaskhanite (Pacifidlog)
Delta Episode done

(Do a world tour of Hoenn basically now)
26 Latiasite (Littleroot Town)
27 Lopunnite (Mauville)

Switch to Acro Bike
28 Absolite (Safari Zone)
Switch back to Mach Bike

29 Manectite (Route 110)
30 Ampharosite (New Mauville)
31 Charizardite X (Fiery Path)
32 Tyranitarite (Jagged Pass)
33 Houndoominite (Lavaridge Town)
34 Galladite (Fallarbor Town)
35 Blazikenite (Route 114)
36 Sceptilite (Route 114)
37 Salamencite (Meteor Falls)
38 Venusaurite (Route 119)
39 Charizardite Y (Scorched Slab)

Do contests and cry
40 Lucarionite

41 Blastoisinite (S.S. Tidal)
42 Sharpedonite (Battle Resort)
43 Gengarite (Battle Resort)
44 Audinite (Battle Resort)

Do E4R2
45 Metagrossite (E4R2)