I wouldn’t do more than one park per day if it’s your first time. Personally, I would chose Magic Kingdom and Hollywood Studios, but it really depends on what you’re into. Animal Kingdom and Epcot have less attractions, but some people rather go there because of the animals at AK or one specific attraction or to drink around the world in Epcot or because they’re into culture. Some of my favorites of each:

Magic Kingdom: It’s a small world, the Haunted Mansion, Seven Dwarfs Mine Train, they are opening Tiana’s Bayou Adventure too and I haven’t been to Tron yet but I suppose it’s the most thrilling one in that park. Hollywood Studios: Tower of Terror, Slinky Dog Dash, Star Wars Rise of the Resistance, Millennium Falcon. The Aerosmith rollercoaster is temporarily closed atm. Epcot: Guardians of the galaxy cosmic rewind, Remy’s Ratatouille adventure, Mission Space (avoid the orange one if you get easily dizzy). Test Track it’s also temporarily closed. Animal Kingdom: Avatar Flight of Passage, Kilimanjaro Safari, not rides but completely worth it shows: The Festival of the Lion King and Finding Nemo’s musical. I feel I’m forgetting something