*gets pulled in by Tress*
Welcome to Dragonmount, Kinslayer.
Stormlight Archive is my personal favorite series at the moment! The world is totally different from our world, with a different ecology, climate and everything, worked out super well, with magic ingrained perfectly into it and the characters are absolutely amazing.
Fair warning though, it's got a very high learning curve because of how much worldbuilding there has to be done, so you need to be ready for that.
As for wheter it's a good idea to start Stormlight Archive, if you're absolutely convinced you'll read it, go ahead! If you're not convinced, start somewhere else, find out Brandon Sanderson is the best author ever, and use that knowledge to get through the hard early part of Stormlight Archive. (note, I actually backtrack a bit on starting with Stormlight Archive later on but I'm not gonna rewrite the whole post)
The easiest starting point for Brandon's books is probably Mistborn. Of all Brandon's works, the original Mistborn trilogy best resembles standard fantasy, and Brandon knows exactly how to surprise you in all the right ways with that. Additionally, the learning curve is much lower - most of the first book is a single storyline, while Stormlight Archive has 3 major storylines and one minor storyline throughout the first book.
You can also start with Elantris, which is a very good book even if it was his debut. I greatly enjoyed reading it, and Brandon tells the story in a great way, with 3 main characters that he rotates through in a set way, giving them a chapter every time, making them interact brilliantly.
What's also one of the most satisfying things about Brandon's books (and for that it doesn't matter with which one of these series you start) is that they tend to have at least one character that just inspires other characters around them.
As for what to read after the first books, the order doesn't matter a whole lot, but you should of course make sure not to read things in the wrong order (so read Mistborn Era 1 before reading Mistborn Era 2). Additionally, I would like to recommend reading Warbreaker before reading too much of Stormlight Archive, as there are a few crossovers. You definitely need to read it before Oathbringer, and preferably before Words of Radiance. Additionally, you might want to read Warbreaker after Elantris and Mistborn Era 1 because Brandon uses them as foils for one another at quite a few points (and that's all I'm going to say about it).
So yeah, unless you really want to read that big Sanderson epic (which can be done, you can even read Oathbringer before Warbreaker, but it will raise a few questions about the history of characters), I'd probably advice this reading order:
Mistborn: First Era
Mistborn: Second Era
Elantris (+Emperor's Soul I think, but I haven't read it myself yet)
Stormlight Archive (note: read Edgedancer (a novella that plays around the end of Words of Radiance) before Oathbringer)
As for the other Cosmere books:
Mistborn: Secret History: Definitely do not read before finishing the First Era (major, like super major spoilers), and you might even want to save it for after having read the Second Era, though it won't spoil anything.
White Sand, Shadows for Silence in the Forests of Hell, Sixth of the Dusk: I haven't read these myself yet, but as far as I am aware it doens't matter too much when you read them exactly. I think that you'd best save them for later, as they're less important to the Cosmere overall.
Oh and if you want to know more about the Cosmere (make sure to at least finish Elantris, Mistborn and Stormlight Archive beforehand though, because spoilers!), go to 17thshard.com, which is basically the Brandon Sanderson version of Dragonmount only people are theorizing even more intensively than the Wheel of Time community has ever done (and that's saying something).