I am sorry about your first betta but I am sure your mum meant well and felt bad about it. My dad doesn't care and if he had listened to me, none of this would have happened. And yeah, Pluto isn't gonna survive the night. :( I have covered his tank to give him peace. It's 9pm and I am dreading waking up in the morning to find him dead but I have my other bettas to focus on and care for which makes it easier to deal with. He is my only veil-tail so if he goes, I will be buying a red veil-tail or one that looks like yours, in his honour.
Have you tried shopping online? I live in a small town, so much of my shopping happens online at amazon. It's cheaper for me that way too and I don't have to worry about fighting traffic.
Pics can be tricky at the beginning. I found it's easier to turn on a ceiling light (for extra light) and take dozens. Odds are they'll be still for one of them! XD
5gal is a good size. You won't have to worry too much about PWC, there's plenty of room for décor and even plants, you can cycle it, and there are a few tank mates that can Btw added (depending on hardness) like a snail or shrimp. Shrimp are great cleaners, but they need plenty of hiding places because some bettas see them as snacks!