@SquirrelJulietGarden provided the boards where you can’t post until you reach a certain Rank. Aside from that, you can post anywhere you wish. Newcomers that are not just bounty hunting tend to post more, I believe, in Beginners & Help and Bitcoin Discussion, but it’s not so much a question of where you want to post but what topics you feel more inclined to participate in, which lead to determining the appropriate boards.

Now it’s true that it is not trivial to participate with some non-trivial comment, and the best way to overcome that is to read a fair share on the topic to gain some background knowledge, and to try to read through the whole thread (within reason) before making your post.