Oh Boom, what have you done to that poor Infernape.
Firstly, can you get to the move deleter (or did you save already in the E4), and do you have any heart scales for the move
relearner? If so, that changes what I'd suggest you do quite a lot. If you can, do the first of any of my either/or suggestions.
Infernape - If you can, get the relearner to teach it Close Combat. If you can't, give it Return instead. Chuck Grass Knot at it as well, either way. Use your PP Ups on Fire Blast.
Staraptor - Get it up two more levels and replace Fly/Aerial Ace with Brave Bird. If you haven't used Return on Infernape, give it to this one, replacing the other of the above (or Quick Attack if you can't delete Fly).
Gyrados - The trouble here is you've given it a load of special attack moves, when it's special attack stat is utterly rubbish. Physical attacks are the way you need to go here. Replace Surf/Dragon Pulse with Waterfall, and relearn Dragon Dance over Dragon Pulse/Hyperbeam.
Luxray - Replace Shockwave with Spark if you can relearn it.
Pupitar - Level it up three more times, teaching it Stone Edge (replace Rock Slide) when it learns it.
Dialga - Replace Dragon Claw and Metal Claw with Flash Cannon and Blizzard. If you fancy a trip, find an old lady in a house on route 210 and get her to teach it Draco Meteor (replace Roar of Time), and buy Thunder from the dept. store.
That should about do it.
Start with Staraptor. Try and hit anything that comes out with Close Combat or Brave Bird. If you can't beat it, switch to either Infernape or Gyrados, depending on strengths/weaknesses. If you can get Gyrados fighting something that can barely hurt it, spend a turn or two using Dragon Dance, and it'll pretty much destroy whatever will come after that. Tyranitar (as Pupitar will become) is your failsafe if the first three fail. It's an absolute beast of a pokemon, and with it, and your newly suped-up Dialga, and the lovely annoying sandstorm effect, they should both be way too strong for whatever's left.
Also, if you come up against anything that's a overly-strong physical pokemon, try switching between Gyrados and Staraptor a few times, and their Intimidate's will stop the enemy Pokemon from doing any kind of damage.
Luxray really isn't that great, but just in case you need a reliable electric move, it'll do.