How do I set up a microsite, what are my options?

I'm currently working on Joomla 3.4.3 hosting via an LCN domain.

I need to create a microsite to promote and event and I haven't any experience with setting one up.

I just want to know whether it's easiest to do it via a sub-domain with another copy of Joomla and my template on it? Or is that a bit overkill, is there an easier way?

Thanks,