I find the constant debate about the ‘best’ order a bit tiresome. It presupposes there’s a wrong way to enjoy fiction. Read what’s available. Skip what’s boring. Life’s too short to treat leisure reading like a mandatory curriculum.
Some people find Asimov's characters flat. His strength is ideas and plot. If you need deeply emotional, character-driven narratives, you might struggle with Foundation in particular. The robot novels have more character work. So if character is key for you, start with the Robot detective series (Caves of Steel). The partnership between Baley and Olivaw has real heart. It's a better entry point for character-focused readers.
For a truly thematic path, follow the idea of 'psychohistory'. Start with the Foundation trilogy to see it as a grand, abstract force. Then read the Robot novels, especially the later ones involving R. Daneel Olivaw, to see how a single persistent intelligence might work behind the scenes to enable psychohistory. It reframes the entire saga as a conversation between collective human mathematics and individual robotic guardianship.
Asimov himself gave conflicting advice over the years. Sometimes he said publication order, sometimes he suggested chronological. That tells you all you need to know: there is no one right answer. Pick a path that seems interesting and just start reading. The connections will reveal themselves in a cool, non-linear way. The universe is big enough that you can't really read it 'wrong'.
Chronological purists will tell you to read every short story in timeline order, including those in 'The Complete Robot'. That's a project. For a casual reader, it's overkill. The novels are the main event. Read the shorts to appreciate the worldbuilding, but don't stress about fitting every single one into a precise slot.
The library hardcovers from the 50s and 60s are where I found most of his collections. They're often organized by theme, not chronology. This is the way they were meant to be read—as curated explorations of a concept. The order within those books is usually thoughtful, building a rhythm. Seeking a mega-sequence across all collections misses the editorial intent of each individual volume, which was the primary way readers experienced them for decades.