New Discussions may had been disabled due to the last round of spambot attacks that took place last November 2016 as I haven't seen any New Discussions started by any New Members. You need to become a full member before you can start a new thread. I've posted the requirements on your wall on what you need to do to be a full member... :)
For any New members who what to get their post count up, the best thing that I would advise you to do is to find threads that may interest you and join in on them or go to the Off Topic section and join in on some of the word/story games over there. The posts made over in the forum section will go towards your post count whereas the posts made on your wall and the Activity Feed doesn't go towards the total post count. Hopefully creating your posts on other threads will also increase your points... :)
In order to be able to posts pictures and have an avatar, you first need to become a full member because as of right now you are considered a new member. New members are restricted to post pictures, links, have an avatar or change one, sending private messages to other members. In order to become a full member, you will need to have 50 points, 30 posts and an account older than 24 hours.
This link here will explain all you need to know on what it takes to become a full member. It also has a full list of badges that you can earn and how many points you get with those badges... http://forums.thesims.com/en_US/discussion/770609/member-or-new-member-everything-you-need-to-know/p1