Personally, I always love drawings of bubbles and how people capture their color and reflections of light. I am by no means an expert on art. However, I would like to offer some critique to help you improve and feel more confident about posting in the Intermediate board.
Bubbles are semi-transparent and shouldn't be fully colored in, even with an airbrush; it makes the border less crisp. The white line isn't really necessary then if the color/highlights are clear enough to show the outline without making it look two-dimensional. Bubbles are spheres so a three-dimensional appearance is what you should try to aim for, but if you can make it realistic in another way, go for it! I also think that just a single bubble may not be quite enough for this board. Try adding a background, even just a gradient or some smaller bubbles to make the drawing look more detailed. Time is also a big factor, so try to spend at least 30 minutes (though most would say an hour or so) on a drawing that you want to be in Intermediate. The longer you spend drawing, the more your effort shows and the better the drawing is.
Many artists on CS have drawn bubbles and have even created tutorials on making them. It may help to look at a few to see how others try to draw them. One good tutorial I found is
here. Try to mix in different techniques to help develop your own style.
I hope to see more of your art soon! I believe, like any artist, that there is always room for improvement. Keep on trying and you will definably be seen on the Intermediate board more often
