No, you wont get virus through wifi, just beware of sites on which you visit, the stuff that you download and other devices that you connect through USB.
Precaution is always better than cure! Get anti-virus installed or you have to go through a lot of trouble to remove it, sometimes you even have to format the system for that, so just protect it!
I tried Kaspersky as it came pre-installed with my laptop but it made my system very slow. I moved to free edition of Avast and have no issues with my system performance now and it offers good protection from virus.