I just beat Brawly and I have a level 17 Grovyle and a levl 13 Ralts. Who should I add between here and Mauville?
Personally, it would be hard to beat Wattson with Ralts and Grovyle. Considering Psychic and Grass type attacks won't do a considerable amount of damage to his Electric-Steel type Magnemite and Magenton. Perhaps, you should look some Pokemon at Granite Cave? Or, Cosplay-Pikachu might be another option.
probably after strength. I've noticed all the old mega stones can be found anytime, with the other ones post game only.
Where do you find Strength? I must've bypassed it sometime (just beat Norman).
I suppose I could pick up an Aron in Granite Cave. What section of the cave can I get one of them?
Strange, I recall receiving it from Brendan when heading toward Fiery Path from Mauville after visiting Vendaturf and getting the Aggronite by rock smashing the rocks in the Vendaturf Tunnel.
edit- Just double checked, I got strength and I'm pretty sure that's how it happened.
I'd try doing the Vendaturf events if you haven't already. Then head back toward Fiery Path and see if Brendan shows up to give it to you. If he doesn't show up before you enter Fiery Path then something's up.
Magikarp is the only Pokemon you can catch with the old rod, right? Or are there others (I know in previous gens there were sometimes)?
More importantly, has anyone heard anything about the method to catch Feebas? I saw a couple posts about it already but I don't think there was an answer yet. The Hoenn dex says Route 119 again but nothing about its rarity or if it's the same as the original games with the Dewford trending saying controlling the spaces it's at.