What's a good way to get a team where lucario is viable?
While I don't think anyone here is going to build you a team, but Mega-Lucario is one of the best offensive pokemon legal in OU currently (if not one of the best ever). The issue is getting Lucario a switch in, as it is quite frail. One way to buy a free turn is through putting a foe to sleep, then switching in. At worst, they'll switch in a pokemon that threatens Lucario, in which case you can just switch it back out. At best, you get to mega-evolve set-up Lucario for free. However, the most reliable sleep moves (sleep powder, spore) got nerfed in this gen such that they no longer affect grass types. Another method is to use Wobbuffet or Gothetelle, utilizing shadow tag and encore/tricking a choice item respectively to lock the foe into a move that cannot harm Lucario. Switch in Lucario, and get a free turn to set-up.
Outside of somewhat gimmicky strategies like that, build a team with members that compliment Lucario. Include things that deal with and kill its checks, set up hazards and support. Rotom-W, for example, could be a good partner because it resists fire and is immune to ground, can have bulk Lucario lacks, and can burn or volt-turn on foes to help Lucario come in. It's also a counter to Talon-flame, a pokemon that can threaten Lucario.
Another method is to treat Lucario as a clean-up sweeper. Build the rest of your team around wittling the foe down as much as possible, then bring in Lucario after one of your pokemon dies (or you get a good chance to switch in) and rip through the weakened team. In fact, you always want to try and save your sweeper for when you've worn down the enemy's team. Trying to attempt a sweep too early, against a healthy foe, is asking for some check to come in and wreck your momentum. A team like this likes having heavy hitting pivots, pokemon intended to come in as a check/counter for something, hit the foe's switch in for decent damage, then switch out. Volt-turn cores do a good job of this since the attack itself switches you out, letting you keep momentum. Rotom-W, Genesect, and Landorus-T are good examples of pokemon that can form such a core. Volt-turn is by no means the only method though; pivots and pivoting are a staple of competitive pokemon.
Another method is Semi-stall, where you use a defensive core and stall tactics early on to cripple the foe, and then sweep using Lucario.
This may not be what you were looking for, but trust me, M-Lucario is so good it's not hard to find a place for it on a team. Regular Lucario is a bit harder to use, but the same principles apply.
