MemberGate is more for a straightforward membership site and works well right out of the box for that purpose.
Youtube, dating sites and any site that has a database directory require specialized setups and databases. MemberGate does not have these specialized setups or databases, so MemberGate could not be used for these types of sites.
If you look at our list of active sites at membergate.com, you will get a very good idea as far as what type of sites can be used with MemberGate and how our clients are using them.
To do a dating site or youtube type site, checkout other sites online that are doing something similar to what you have in mind. You can often find what software they are using by looking down towards the bottom of the screen or looking at the source code of the site's pages itself.