All releases from Return to Ravnica forward are legal, provided those sets were once legal in Standard. Click here to see all card sets currently legal in Pioneer.
Pioneer fills the gap between Modern and Standard—it's an approachable way for players to keep using Standard cards after rotation.
Minimum of 60 cards with no maximum, as long as you can shuffle your deck unassisted
Up to 15 cards
No more than 4 of any individual card in your combined deck and sideboard (with the exception of basic lands).
See this page for a list of banned cards.