After getting your second badge in Sapphire, a good idea would be to teach a Pokemon HM Flash (obtained from a Hiker in the cave north of the town) and search for Steven Stone in the same cave. Next go to Slateport City via Mr. Briney and deliver the Devon Goods (I think that's what it's called)
Tips: Catching an Aron could prove useful considering it's a steel type.
An Escape Rope would be useful in the cave but I think there's one in there.
the third badge in sapphire is at mauville city(north of slateport city)
In Pokekon Sapphire, you get the 5th badge after defeating your opponent in a Gym Battle at Petalburgh.
in lavarage town
The fifth badge is in Sootopolis City, you need Surf, Dive, and Whirlpool to get it
Flannery's gym in Lavaridge Town.
the third badge in sapphire is at mauville city(north of slateport city)
It is the balance badge where you fight Norman(your father) in Petalburg City .
Go to lavaridge town for your next badge.
Petalburg City.
You have to beat flannery
you can get the fith badge by going to petalburg the poke gym there.
You get the third badge in sapphire when you get to Mauville. You have to battle Gym Leader Wattson in the Mauville City Gym.
In Pokekon Sapphire, you get the 5th badge after defeating your opponent in a Gym Battle at Petalburgh.
in lavarage town
Have a ruby or another sapphire trade you a legendary!
the 4th badge. it also is the horse jumping through something with a ball in the middle
Go to sootopolis city for your next badge.