They're all fantastic, so I'd totally recommend going through the whole Cosmere. If you just want to do Mistborn, that's totally cool, but if you go through the whole Cosmere, I generally recommend publication order because books frequently build off of or highlight how the metaphysics has evolved in the past, so you're learning how things work at the same time he's making use of it.

The only reading order exception I recommend is MAYBE Eltantris. It's the very first Cosmere book published, and while it's still a solid book, it's his first one, so his writing isn't quite as good yet. Still great, just has some fierce competition from the rest of the Cosmere. I generally recommend the Mistborn trilogy first to set the hook, and if you're all in, read Eltantris. If you're still not all about it yet, read Warbreaker first. Warbreaker is a lot of people's favorite, and it's still a really early book that fits around there in the publication order anyway.