Well, more bandwith is necessary if your site is very popular and if your sites hits many visitors every day. Otherwise, you don't need to concern about bandwith and even 5 GB data transfer or bandwidth is enough.
Anyway, there are many free hosting companies out there for you which are giving away 10 to 40 GB bandwith. One of them is x10hosting.com (45 or 10 GB depending upon the plan you choose).