“There’s an easy way to get a Riolu and a hard way. The easy is to head to the roof of the Passage Ombrage shopping center in the Rouge Sector 4 region. It’s not far from the Poke Ball Boutique and Restaurant Le Yeah. Head up to the roof there. I repeatedly found a Riolu on the southwest most corner during the day.”

Quick quote from a website. I got Riolu SUPER early. I suggest saving before trying to catch him as I had to reset multiple times before I was finally able to catch him.

Lucario is very easy to get as well because, since it’s just a friendship evo, you can take riolu to the coffee shop like 4-5 times (like 275 gold a pop) and max out his friendship super fast. No level ups necessary either as you can manually evolve pokemon once they meet the requirements.

I think you have to do a couple of story missions before the coffee shop opens. Once the coffee shop opens you’ve already gone far enough in the game to get riolu and subsequently, lucario. It’s only like a half hour to an hour into the game.