Aquariums: Help! Got Betta at Secret Santa Party

Question-

Any advice for fish-in cycling for a newbie?
Would using the “betta water” they sell at the pets store be any help? Or is that just a waste of money?

Details/backstory-

My sister ended up with a betta fish at a Secret Santa party. She’s never had fish before and I’m a very new beginner myself (I literally got my betta yesterday after doing a fishless cycle and I had some issues and had to do a post for myself [thanks to all the wonderful folks who helped me!!]). She’d like to keep the fish, so I’m trying to help her with my limited knowledge.

She’ll have to do a fish-in cycle. I researched it a bit and it seems like doing a 5x dose of Prime every 24-48 hrs (correct me here if I’m wrong) plus a product like Stability is the way to go. Along with daily testing and water changes if the ammonia/nitrites go too high (1 or 2ppm, I think? Since the Prime is supposed to detox up to 5ppm?). I’m basing this off of a YouTube video, so pls feel free to correct or give me advice on this!

I just learned they sell “betta water” at big box pet stores. Would it be a good idea to buy this to start off her tank? She’s on a well, so chlorine shouldn’t be an issue. Idk if this is just a waste of cash though.

I’d share some of my cycled water with her, but my tank is so new and the cycle so fragile I don’t think it’d be a good idea. I don’t want to compromise my own betta. 🥴

Thanks in advance for any help! Photo of her little guy. I told her to keep him in the container overnight and we’ll figure this out tomorrow.