Here's an ideal itinerary for 3 days in Doha:

Day 1:

• Start your day with a visit to the Museum of Islamic Art, which houses one of the world's most extensive collections of Islamic art.
• After that, head to Souq Waqif, a traditional market where you can find everything from spices and textiles to souvenirs and handicrafts.
• In the evening, take a stroll along the Corniche, a waterfront promenade that offers stunning views of the city skyline.

Day 2:

• Begin your day by visiting the Katara Cultural Village, a cultural hub that showcases Qatar's heritage and traditions through art exhibitions, performances, and workshops.
• Next, head to the Pearl-Qatar, an artificial island that features luxury shopping, dining, and entertainment options.
• In the evening, catch a show at the Qatar National Convention Centre, which hosts a variety of events ranging from concerts to conferences.

Day 3:

• Start your day by exploring the Aspire Zone, a sports complex that includes facilities for football, tennis, swimming, and more.
• After that, visit the Sheikh Faisal Bin Qassim Al Thani Museum, which houses a vast collection of artifacts and artworks from around the world.
• In the evening, head to the top of the Torch Doha, a skyscraper that offers panoramic views of the city, and enjoy a meal at its revolving restaurant.

Of course, this is just a sample itinerary, and there are plenty of other things to see and do in Doha. Let me know if you have any specific interests or preferences, and I'll be happy to tailor the itinerary accordingly.