What level do I need to be to beat dialga I am riolu and my partner is..

In my past experiences, I took on Primal Dialga at level 40. I used Squirtle and Treeko then. If you have Riolu and Pikachu, you probably could do the same. Just make sure you load up on reviver seeds, oran berries, totter seeds, sleep seeds, stun seeds, and maybe 2 or 3 max elixers in case Diagla's pressure makes you lose all your PP. As for moves, Riolu should have Force Palm, Dig(if possible),Aura Sphere(not sure about this one),and any other fighting type attacks. Swords Dance also comes in handy. As for Pikachu, Thunder Wave would help, Thunder Bolt, Dig(not sure if Pikachu can but you can try), agility and any other ranged attack or electric attack. Set him to use Thunder Wave first to paralyze Dialga. Then the two of you can keep on attacking him until he returns to normal. Be careful though, his roar of time attack could kill you in one attack, so use reviver seeds. Stun seeds come in handy when you want to heal by wasting turns. Just throw it at him and heal while he's petrified. Totter seeds help only to have him move away, but he can still use roar of time so be careful. Sleep seeds put him to sleep, letting you attack him without taking damage. I hope this helps a lot.

I Have just done this one and you need one or two reviver seeds and oran berries and most of all you need 2 Violent seeds, teach riolu brick break or summat like that and not sure about pikachu. If pikachu can learn briack break then you will be ok. I battled dialga at 44ish and I had no problem with these items I just used brick break and Cindaquil used flamethrower and it only taken 2 shots from me and 3 from cindaquil, he really isn't that hard to defeat

I beat dialgia at level 43 or so I only had 1 reviver seed and used mostly sleep and totter seeds.