I might not get any PhD offers this year. I would like to apply again , what can I do to maximize chances
You've got a couple of options


See what happens with the current applications.  You may be surprised.
Try to get a job as a researcher at your current university.  If a prof. has worked with you and can vouch for you this will be much easier.
Have really awesome GRE or equivalent scores.
Cast a wider net.   Searching "top 10" on this site gets you 200 results!  You may want to apply to schools outside of the top 10 in your field as this seems to be the cut-off most well-qualified applicants use.