If the avatar works you will not need to keep creating posts since it will show up on your existing one.
What size photo are you trying to upload? It has to be small to work - less than 160 x 160 pixels and less than 15.62k. If you are not computer savvy and need help downsizing it, attach it to this thread and I can make it fit.
If you're simply trying to get through double secret probation by creating posts, you may find yourself a statistic along with the thousands of kids from Nigeria that try to get past our crack team of moderators with promises of money from a dead millionaire uncle's estate.
All kidding aside, welcome.