Bali is famous for its picturesque waterfalls. Wherever you stay on the island, you will easily come across one. For a better experience, it is usually recommended to visit any waterfall early in the morning to avoid crowds and too much light/heat. We visited Sekumpul and Kanto Lampo ourselves and enjoyed both.
Bali’s most famous rice fields are Tegallalang and Jatiluwih, both of which are close to Ubud. Tegallalang tends to be crowded, so I recommend going there to watch the sunrise. If you are lucky enough in meeting some locals, just ask and they may take you to some less crowded places.
I definitely recommend spending a few days in Ubud and then exploring the surroundings. The Sacred Monkey Forest is a beautiful place where you can get close to these little monkey creatures.
The beaches in Bali itself are not the best. However, you can choose to take day trips or multi-day trips to the surrounding islands, all of which have stunning white sand beaches. Whether you choose to visit Penida, Lembongan, Ceningan or Gilis (Lombok), you are sure to find a white sand paradise.