route 25
After you defeat Misty, You can go catch suicune by Bill`s house.
You can go and challenge other Gym Leaders in the Kanto region, such as Brock.
you go to the power plant talk to everybody there go to mistys gym after that and there will be a man in black there beat him in a battle and then go to the side of house there you will see misty.
Once you fixed the Power Plant, go to the end of Route 25. Talk to Misty and she'll return to the gym. Then you can beat her. (She uses water Pokemon so I suggest you use grass or electric Pokemon.)
beat the league
He disappears until you beat the Pokemon league again.
you go to cerulean city and beat misty.
Earn the national Pokédex, go to the mountain where Red is and beat him.
You should go to Pewter City next if you have beaten 5 Gym Leaders so far. If not, go and challenge another one of the first Gym Leaders first.
After you beat all of the kanto gyms, go to cerulean city and go to where you saw misty with her "date". Suicune will be waiting there.
Once you beat the Pokemon League at the Indego Platue, you will be able to go to Kanto and see Misty.
beat the game, and go to misty's town. and go to the cave