Is finding a teacher necessary to practise dhamma? Many times I hear people say it's neccessary to have a teacher. I'm a bit lost as how one finds one. I've been to sanghas, talks, retreats but haven't met anyone who ive felt I could approach and ask to be my teacher. The Buddha never had a teacher. If he became enlightened without one then I presume anyone can. I find that the more people I talk to the more confused I become because so many people have so many conflicting condradictive perspectives.  From what ive heard and read if you sit and practice mindfulness of breathing etc you will gain insights into the true nature of reality.
Do you need teacher to practice Buddhism?

No you don't - but you need to know how to practice. And with so much contradicting information about Buddhism on the Internet and in books, to know the right practice requires insight into principles of Buddhism. Once you understand the principles, you can see for yourself which practice is real and which is a confused echo of real.

Do you need teacher to gain insight?

No, you don't. You can piece the puzzle together from books and videos, and integrate it all together into your own insight.

However, that requires an extremely good memory, very good intuition for the implied/inferred meaning, and a very good ability to connect the pieces of information that you may have received in different context, many years apart.

In real life, I'm a professional software architect at a large US company. As a software architect, I have an extremely well-developed capacity for remembering thousands of little pieces of information that I don't fully understand, and then slowly integrating it together into a meaningful whole that I can reason about and often see problems that others can't see.

And even with this ability, it took me almost 15 years of studying Buddhist texts, across Theravada, Mahayana, Vajrayana, Zen - to have even the basic understanding of how it all fits together. I'm not talking about the theory, I'm talking about understanding the basic idea, the framework, the "spirit" of Buddhism. Knowing the theory without understanding the "spirit" is useless. Someone like that can quote the texts but can't explain it in his own words. It's only when you get the "spirit" is when you "find the ford" and become "independent of others in regards to the Buddha's message" (the label on my profile).

Anyway, imagine my surprise, when after those 15 years I went to a live Zen Master and from his few replies and the overall behavior realized that he had a perfect intuitive grasp of all the principles that it took me 15 years to even begin to discover! I could have saved so much time! More than that, in two years of practicing meditation under Master Shin, I learned more about the real meaning of Buddhism than in 15 years of reading books.

Alternatively, you could in theory repeat Buddha's path and figure it all out in meditation, without any guidance or books, - but unless you're a genius like the Buddha (although as @PeterJ pointed out, even the Buddha had some teachers), the chance you'll strike gold is one in a billion. 

So, do you need teacher to gain insight? No. In fact, it is impossible for any teacher to give their insight to someone. Insight is something that happens in your head, as you build the puzzle and see what it means in real life. But a live teacher who already has the insight, can save you years or even decades of time you'd either spend accumulating theory (like I did) or stumbling in the dark.

So even though I myself spent 15 years studying books and only 2 years learning from teacher, and now 6 years practicing on my own again, when anyone asks this question I always say: yes, go to a live teacher. If you can't find a live teacher, then at least talk to me. I will do my best to share as much insight as I can. Do not repeat my path.