SSL will definitely help make your visitors browsing experience a more secure one. It encrypts data to-and-fro your visitors' browsers and your server. So SSL is ideal for all traffic, but especially things like login pages (where username and passwords are sent) or checkout pages (where credit card information is submitted).
Any of the major Certificate Authorities can issue you a globally trusted ssl certificate, but since you are on the ssl.com answers site, you can try out https://www.ssl.com/certificates/basicssl/buy
I would definitely recommend you get your own certificate since you are currently using another website's ssl certificate, and you will get the 'This site is untrusted' pop up: