Mauville city.
1950s
you go to victory road
u have 2 get the 17 badge after go to cinabar island and talk 2 the only man outside of the Pokemon center hell look 2 see how many badges u have if u have all but the last badge hell go back 2 the gym in and u can battle him be careful hes tough(:
go to the north rustboro (city where you get the rock badge) where the woman is, go to the beach and surf between the light brown rocks. You find a forest with 2 trainers and some weird looking berries, go in.near the karate guy you find some stairs and a pokeball, in that pokeball is tm1
Type 'battle gallery' in the search place. go 2 the page. click on capt reynolds. voila get the badge
go to the little house in celestic town.make sure your all your badges have 4 sparkles on it.then stand in front of the little house and follow this gym badge pattern: badge 2; badge six; badge 5; badge 7; badge 3;............................................. man i forgot! just go to youtube and type this:pokemon diamond-how to capture celebi and look for how to capture celebi(no codes!) WARNING!THE VIDEO CAN GO A LITTLE FAST DURING THE BADGE PART SO HERE'S A TIP: pause each time the video hits a badge.
Go to Mossdeep city and beat the gym.
u go 2 farawayland
go 2 mt.cornet top {beware u need 2 beat Cyrus there}
go to Eterna city and defeat the gym leader(she has grass type pokemon).
u must go 2 cianwood city get the medacin and bring it to the light house
get the hm waterfall (forgot were u get it) and go 2 the Pokemon league climb the waterfall and go in 2 victory road 2 the other side! Hope i helped! : )