Collect Kanto Badges
Leave New Bark Town and board the S.S. Aqua to travel to the Kanto Region. Both the cities and gym leaders are duplicates from the earlier Pokemon LeafGreen and FireRed games. Although the leaders have the same Pokemon, they're much more experienced. Unfortunately, most of the other trainers in the region are still low level.
Become the Kanto League Champion
Explore the Kanto region until your Pokemon party and legendary birds are level 50. Visit a Poke Mart and stock up on healing potions and status remedies. Fly to Indigo Plateau and take the Victory Road. Your Pokemon party will need to have the following TMs: Surf, Strength and Waterfall. Before encountering the Elite Four, your Pokemon should be at least level 53. Afterwards, you become the new Kanto League Champion.
Catch all the Legendary Pokemon
Excluding the birds, Soul Silver̵7;s legendary Pokemons include Lugia, Suicune, Lapras, Raikou, Entei, Ho-Oh, Mewtwo, Groudon and Latios. After defeating the Elite Four and becoming the Pokemon League Champion, you will encounter legendary Pokemon with greater frequency. Save your game before battling any of the legendary Pokemons. Use powers such as False Swipe and Ancient Power to weaken a legendary Pokemon and throw ultra balls to capture it.
Complete your Pokedex
Between pursuing the legendary Pokemon and collecting the Kanto Badges, your party will travel through both the Kanto and Johto regions. Battling every trainer you encounter will complete your Pokedex. After capturing all sixteen badges, you can receive the gym leaders̵7; phone numbers. You can call any leader for a rematch. All gym leaders will have changed their Pokemon lineup since your last encounter.