Question: “Should I devote myself to one form of Buddhism (ex Tibetan Buddhism) or can I just read Buddhist writings from different cultures and make my own interpretation of Buddhism?”
Each “form” of Buddhism is almost very different as far as “important” teachings, rituals, and main sutras. Tibetan Buddhism, Vajrayana, is probably the most different of all the Mahayana forms. Vajrayana is the most culturally mixed form of Buddhism because it’s half buddhism and half local religion (which are forms of Shamanism and witchcraft). Then you have Japanese Buddhism (Zen being the most popular) that also mixes with the local religion, Shinto. Chinese Buddhism, Pure Land specifically, is also very “popular” around the world.
In the West you’ll probably notice the majority of temples are Tibetan or Vietnamese. Vietnamese Buddhism mostly follow the Tiantai (or Tendai), using the Lotus Sutra as their main text (the tradition I follow).
You don’t have to follow or devote to one particular form or school, especially if you don’t attend a temple for teachings. As a layperson, you have the freedom to pick and choose what sutra you feel is most important and stick with it for years and years, if not your whole life. You devote yourself to a sutra, not a tradition.
Smile and be well!