It sounds like it might be ready (I'm a sourdough newbie myself).  I started out making Sourdough english muffins (I used this recipe) because it was fast and easy and you can literally watch the leavening take place.  If your muffins rise during the fermentation stage, your sourdough is doing it. 

There is some chemical leavening in the form of baking soda, but that doesn't really happen until the heat is applied.  It will really help you build confidence in your starter without a huge outlay of time and ingredients.