What do you do after you defeat Pokemon trainer red?

After you defeat him, you go to Pallet town & pick up your 1st generation Pokemon starters in Prof. Oak's lab.

Then, go to Saffron city, & go to Silph Co. & look for steven, once you meet him he will say to pick a shard.

Make sure you have space in your team, so take only 5 Pokemon w/ you.

there is a blue shard, a red shard, & a green shard.

If you choose the green shard, then you get a treeko

if you choose the red shard you get a torchic

If you choose the blue shard, you get a Mudkip

Then, go to Pallet town, Mr. Pokemon's house, will give you the Red Orb (Soulsilver) or the blue orb (heartgold) you can go to the cliff cave in route 47 & fight Groudon(soulsilver) or Kyogre(Heartgold)

If you have both Groudon & Kyogre, then go to Prof. Oak's lab, he will tell you a story about both Pokemon, then, I think it's he that gives you the green orb, if he doesn't then go to Mr. Pokemon's house, then he will be the one that gives you the green orb, when u get the orb, go back to Cliff cave, & your level 50 Rayquazza will be waiting for you.

If you forgot where mr. Pokemon lives, then go to Cherrygrove city, go to the house in the Northern end of Route 30, don't go to the house closest to the city, because that's not Mr. Pokeon's house.