If you don't exactly know what EVs are, this thread will help you get all the information about them you need: https://pokemonrevolution.net/forum/viewtopic.php?f=123&t=15966
So let's begin:
Kanto
HP
Viridian Forest
Caterpie (1 EV) (Morning, Day)
Route 2
Caterpie (1 EV), Hoothoot (1 EV) (Night)
Route 3
Nidoran-F (1 EV) (Day), Jigglypuff (2 EVs)
Mt. Moon
Clefairy (2 EVs)
Atk
Route 22
Mankey (1 EV)
Mt. Moon (B1F)
Paras (1 EV)
Route 4 & 8
Ekans (1 EV) (Morning, Day)
Route 12
Bellsprout (1 EV)
Rock Tunnel
Machop (1 EV), Mankey (1 EV)
Route 12
Weepinbell (2 EVs)
Victory Road
Machop (1 EV), Machoke (2 EVs),Arbok (2 EVs), Primeape (2 EVs)
Def
Mt. Moon
Geodude (1 EV)
Route 8, 9, 10 & Mt. Moon
Sandshrew (1 EV)
Rock Tunnel
Geodude (1 EV),Onix (1 EV),Graveler (2 EVs)
Route 21 (Grass)
Tangela (1 EV) (Day)
Cinnabar Mansion
Koffing (1 EV),Weezing (2 EVs)
Victory Road
Onix (1 EV), Geodude (1 EV),Marowak (2 EVs)
SpAtk
Route 6
Psyduck (1 EV), Golduck (2 EVs)
Route 24, 25
Oddish (1 EV) (Night, Morning)
Pokemon Tower
Gastly (1 EV),Haunter (2 EVs)
Route 12
Oddish (1 EV),Gloom (2 EVs) (Night)
SpDef
Route 11
Drowzee (1 EV)
Route 12 & 13
Venonat (1 EV) (Night)
All Surfing Routes
Tentacool (1 EV),Tentacruel (2 EVs)
Spe
Route 1
Rattata (1 EV),Pidgey (1 EV)
Viridian Forest
Weedle (1 EV),Pikachu (2 EVs)
Mt. Moon
Zubat (1 EV)
Routes 5 & 6
Meowth (1 EV) (Night)
Diglett's Cave
Diglett (1 EV),Dugtrio (2 EVs)
Route 10
Voltorb (1 EV)
Johto
to be continued...