As I live in an extremely Christian centered country, and am still a closeted non-christian (if that makes sense), it's hard for me to just join a temple (there are none) or a community/sangha. Is it very important that I do, or can I practice Buddhism on my own?
You don't have to join a physical Buddhist community or temple. Instead you can use online resources for learning and be part of virtual Buddhist communities on the Internet. You can also practice the Noble Eightfold Path on your own.
The Basics of Buddhism podcast series by the Buddhist Society of Western Australia (BSWA) seems to be good. Ajahn Brahm, who features in some of these podcasts, is also a famous speaker on Youtube.
Tricycle's Buddhism for Beginners has some nice articles.
If you want to feel close to a Buddhist community, watch the live and recorded videos of the BSWA on their Youtube Channel. During the live sessions, you can submit questions. Sometimes they have live events like the five precepts initiation ceremony on Wesak Day and the occasional monk ordination ceremony.
You can learn the basics of Buddhist meditation as taught by Yuttadhammo Bhikkhu either using the booklet or the Youtube videos. You can join the online meditation courses also, where you could have interaction with other course participants.
When you want to deep-dive into the teachings of the Buddha, use the accesstoinsight.org website's Self-guided Tour of the Buddha's Teachings. The book "In the Buddha's Words" by Bhikkhu Bodhi is also highly recommended.
And of course, Buddhism SE, SuttaCentral and DhammaWheel are a few other online Buddhist communities you can participate in.