You can begin trading without increasing your permission levels.
There are actual quizzes where you need to answer them correctly - and the matter is not trivial if you want to really contribute - to show your competency level, which will increase your permission level. As your permission level increases, your ability to make edits here increases. You may take the quizzes and advance as high as Level 6 right away, but to advance to the next two levels, you'll need to make a lot of those needed edits, add images, and add checklists, to gain points to achieve those higher levels.
-- Dan --
Note: Please see my profile for more info regarding trading (section updated 10/25/2023). I have added a large portion of my inventory to the site, and currently have trading turned off (details are in my profile). I have (finally) unearthed my 2 very large boxes of Star Company minor league sets and they are available (email for details).