Indeed you'll need your poke to be around lvl 80-85 for kanto's e4.
However, some pokemons like gengar can almost solo It if they are lvl 90-95. You can still buy one to another player if you're not patient enough to train it yourself, that will save you a lot of time.
And don't forget to buy a bunch of potions and revives, you'll need it :Grin: .