How do I go about sorting out a holiday on my own, and where would be good?

Hi everyone! I’m a student, and I’ve finally got to the position where I actually will have a job during the holidays. While I plan to stick most of what I earn into savings, I really feel like actually doing something with some of it and going abroad on my own for a couple of days. I’ve travelled with a friend before but never on my own, and I’m just wondering how exactly do I go about figuring out what flights/hotels are good or feasible, and what else I will need to consider to work out a rough budget? I’ve never done this before, but I feel like surely being a student is the best time to do something like this after working for most of the admittedly very long holidays.

On a separate note, does anyone have any good recommendations for places? I’m into cities where I can amble around going to museums and spending most of my budget on nice food, but I also love the beach. I’m not super into nightlife but I do like exploring nice bars, and I’m a lesbian so I’m trying to narrow down to both places which are safe and which actually have a cool gay scene (for example, I‘ve been considering the idea of Chueca in Madrid). I’ve been thinking Madrid, Málaga (I speak Spanish so I’d love to explore more in Spain— Barcelona and San Sebastián are some of my favourite cities I’ve ever been to), Amsterdam, but if anyone has any cool city suggestions I’ve missed please do say!!! Thanks for any advice :)