Veronica Roth is best known for the Divergent trilogy, and the order there is straightforward: start with 'Divergent', then 'Insurgent', then 'Allegiant'. After that, there's the companion collection 'Four', which is a series of short stories from Tobias's perspective, set before and during the first book. Some people read that before 'Allegiant', but I think it works better after the trilogy—it adds depth but isn't necessary for the main plot.
Beyond that, she's written two books in the 'Carve the Mark' duology. You'd read 'Carve the Mark' first, then 'The Fates Divide'. Those are in a separate universe, so you can tackle them independently. I wouldn't mix reading them with the Divergent books, the tones are pretty different.
She also has a couple of standalone novels. 'Chosen Ones' is an adult fantasy about what happens after the heroes defeat the big bad. It came out after her YA work. Her latest is 'Poster Girl', a dystopian novel, also for adults. There's no connection between any of these later books, so you can read them in any order, really.
Honestly, the only tricky part is 'Four'. Everything else is either a clear series order or a standalone.