Yesterday one of my friend john told me about registry cleaners and said that registry cleaner is necessary for the good performance of my PC.
So I am asking that is it good to get a registry cleaner software or I do not need to get it.

Almost needed... but caution!
 
I've tried almost every freeware 'reg cleaner' in the last few decades. Most remove stuff that you don't want removed; windows settings that you like, but which are not defaulted by MS.
 
Generally I like (freeware; not tricky gotcha's) the frequently self-up[censored], when you are on the internet. Only one that know know does that: "Advanced SystemCare Free". Most reliable apps are underpowered, so spe[censored]t problems need rare, speciliased apps. IMO: "Registry Crawler" is old, but it removes very particular rubbish I find.
 
Don't go for the one Advanced SystemCare with added-on virus protector. Keep your firewall, virus protector independent & free. Also frequently self-up[censored], when you are on the internet: AVG, Avast, Avira (anti-virus) & IMO Comodo Internet Security.

Now I am using a registry cleaner.It is working very fine.Now my computer's game performance,boot up speed and applications start up speed is improved.
I love it.

Yes it is needed, once you run it, you will get the entire cookies, temp and other registry files that has no requirement to be kept. So, download it and use it regularly, performance of your PC will definitely be improved.