EV training is hard enough when the Pokemon you are looking for is spread around the map. So I have compiled a list of places that are best to train and what Pokemon you should train on. Link to how many EVs each Pokemon gives can be found here
https://pokemondb.net/ev/all
There is a way to EV train by using gyms. Put the Pokemon that yields the EVs you want in the gym and train it, but using a gym to your advantage may not be available for you or others
----------=HP=----------
Go to
Spawn and kill these Pokemon
Caterpie
Nidoran (Female)
Nidorina
Clefairy
Clefable
Jigglypuff
Wigglytuff
Slowpoke (if you see them)
Lickitung
Chansey
Kangaskhan
Snorlax
----------=Attack=----------
Go to
Smog Town and kill these Pokemon
Ekans
Arbok
Nidoran (Male)
Nidorino
Paras
(Optional, gives 1 in Defense)
Parasect
Bellsprout
Weepinbell
(Optional, gives 1 in HP)
Muk
Gyarados (if you see them)
----------=Defense=----------
Go to
Petra City and kill these Pokemon
Sandshrew
Sandslash
Geodude
Graveler
Onix
Cubone
Marowak
Rhyhorn
----------=Special Attack=----------
There are two options of places to train
Mystical Keep
Psyduck (if you see them)
Golduck (if you see them)
Abra
Kadabra
Jynx
Amethyst Town
Gastly
Haunter
----------=Special Defense=----------
Again you have two options here
Any route with water
Tentacool
Tentacruel
Seel
Dewgong
Mystical Keep
Drowzee
Hypno
Mr. Mime
----------=Speed =----------
Go to
Spawn and kill these Pokemon
Weedle
Pidgey
Pidgeotto
Pidgeot
Rattata
Raticate
Spearow
Fearow
Meowth
Persian
Magikarp (if you see them)
(Optional, gives 1 in Attack)
Tauros
Aether Village
Pidgey
Pidgeotto
Pidgeot
Spearow
Fearow
Zubat
Golbat
Snowtip
Magikarp