Product Recommendations

You can play D&D for free (see this page for details), but if you want to go to the next level, consider these resources...

Official Resources for D&D 5th Edition (2014 rules)

Essentials Kit (the very minimum)

Starter Set (a little more)

Player's Handbook (for the enthusiast)

Dungeon Master's Guide (for DMs)

Monster Manual (book of monsters)

Xanathar's Guide to Everything (expanded options and rules)

Tasha's Cauldron of Everything (more expanded options and rules)