Lucario is listed under fighting type. Therefore, the only super effective types with be flying, psychic, and fairy.
First, the best Pokemon to have as a mega right now, is Slowbro. You should really practice on previous stages to level it up and make it stronger - or leave it (your choice)
Next, the 3 support Pokemon. I can't calculate exactly what damage each Pokemon does, but it seems like your 3 best Pokemon are azumarill, celebi, and swirlix. (These might not be your strongest, but you should choose the 3 types suggested and go on with that).
Now, using these Pokemon, challenge lucario once. Determine how fast you can beat if. If you can't, you know that you would have to buy power ups (from the store - using coins), or go challenge previous Pokemon to make them stronger - exp. boost will help. If you can beat him - but in a short time - don't worry. The point is, try to get lots of high combos. This way, even if your capture rate is between 30%-40%, don't use a great ball - unless you want to. Because of this, your chances are much higher to receive it, but it might take some practice - that takes a while. But, this also saves you a lot of coins.
This is my personal strategy. But, you can add extra or adjust it - doesn't matter with me.
Hope I helped! :)