Solo trip to new york

Any solo travelers? I never done much and it is kinda scary but I can’t wait around my whole life for someone else to be ready to do things with me. I want to see a lot of places and New York and California/Vegas are my top places I want to go first. I’m planing a trip to New York first since I’m in PA. See how i do and than Vegas possibly for my 25th birthday (in June) next year. (Just wanna make sure I have a lot of money to go with) any opinions or advice? What’s the best way to find out best places to stay and things to do around the city/state ik traveling to. Been trying to figure out New York but not much luck just yet