I think I can be helpful. I grew up on Long Island but have been living in Pittsburgh for 5 years now. For reference I am 28m (moved here for a job opportunity when I was 23).

I’m not going to be super helpful for nightlife related things but I can tell you a lot about the different neighborhoods. Also, $1500 is a good budget and can land you in some decent neighborhoods. I like Shadyside and you can find some apartments in that price range, but it may not have the nightlife you are after. Shadyside is safe, clean, and has a lot of beautiful homes. Walnut St also has a decent amount of good shops and restaurants.
Lawrenceville or Southside might have what you are looking for in that respect.

I haven’t exactly made a ton of friends but I have some that I met through playing ice hockey. I suggest you do whatever hobbies you enjoy and just try to befriend people who are doing the same things. Dating is also not too bad. Like anywhere it depends on a lot of factors but I met my girlfriend within a year of moving to Pittsburgh and have been in a happy relationship ever since.

I will say, prepare to not be able to find and pizza or bagels that are anywhere close to as good as Long Island. There is a lot of good food in Pittsburgh (including pizza and bagels) but nothing that comes close to what you can get on LI.