Hey where would be the best place to train before the beating eliet4. ..

Your Empoleon and Dialga are decent for the E4. You might have trouble with the fourth member and champion, but other than that, those two are okay. The others on the other hand, like you said, are undertrained.

My advice is to train them where there are wild Pokemon AT LEAST 5 levels higher than you. With Alakazam, Roselia, and Luxray, your best bet is the Victory Road. I'd use Alakazam against Golbat/Zubat, Roselia against Graveller, and Luxray against water Pokemon [obviously found in the water].

You can start there. Once you get stronger, you can start battling the E4. There, you're bound to get some GOOD experience. Once you get stronger, you should be able to defeat more of the E4 little by little. Eventually, you'll beat the champion, who has level 60 pokemon. Her highest leveled Pokemon is level 66, just so you know, so be prepared.

The best place to train is enbetween victory road and that city I can't remeber it's name. You will need the vs. Seeker wich is obtained from dawn (female charector or if you are the female charector then the male charector). And here is a hint(you need Pokemon with 1 hit ko's for the champion).

Evolve roselia and train in the victory road with an experience share that I forgot where you get it but you can check the faqs to find exp. Share if you don't have it

Um try re-battling the people on the path to the elite 4. The water path, people are pretty strong there.

-Shadow Cresselia

On victory road. Those are the highest leveled Pokemon before the elite 4.

I would suggest battling on victory road and if youre not prepared for that then you can put some in the Pokemon sitting place in solocean. You can also use the vs seeker to rebattle people wherever you please.