Suggest me

My friend had created a youtube channel and she is curious to know what kind of content she should create to get more subscribers. Do you have any suggestions? I am looking for your reply.

Do you know about bus tours from ny?

There are a lot of ways that will prove beneficial to get more subscribers. Let me share one link here which will prove useful for your friend.

https://backlinko.com/how-to-get-youtube-subscribers

Have you ever tried this? Is this really worth while or not?

I am glad for your friend and he is ready to mingle into the world of Youtube. Regarding suggesting what kind of content he should upload, I would say that is very personal and it totally depends on her interests. What she will do according to his passion will be more viral and people will tend to engage more with. But I can give a click to you just have a look at these popular categories that are in trend these days. Maybe you could suggest something to her according to her interest. 
Popular Categories:
Travel Vlogs 
Cooking Tutorials
Fashion Tips
Tech Reviews
Educational Content

And as Andy suggested in his post Backlinks and SEO this suggestion could be beneficial but only if applied correctly. However it takes time if you keep uploading useful contents with consistency. 

And last but not the least, bus tours from New York, there are many options available according to her interests. It oould be great opportunity for her creating a content regarding travel and tours as there are city tours, tours to nearby attractions or even mutli days tour to other states, That would be so much fun though.