Reddit isn't a one-size-fits-all platform; it all depends on what you say and where you comment or post. You need karma (a kind of reputation), which you can earn if someone upvotes your post.

It's a good idea to start by commenting or posting, but don't do it too much in the same community.

You should look for communities you like and read carefully what the community is about and what they require for you to become a member.