Some people earning huge from fiverr and some people doing nothing. It depends on few factors –
01. The work you are offering has good demand or not
02. How much competitive it is
03. Do you have good feedback
04. Are you active and delivery of work in time
Other issue may be same work is not always popular.
It is hard to say, fiverr can be a fully earning site where you can depend, rather you work on other platform also and make sure this is enough to earn and support your expenditure