They're both probably pretty equal. I'd go for Mitsumata just because it's closer! Is it enough for me to buy this package? FYI, I do not have any equipment like a glove, a knit cap, etc.
No, the package is only for jacket and pants. It doesn't specify on the English page, but in Japanese it says グローブ・ゴーグル・帽子のレンタルはございません。They don't rent gloves, goggles, or hats.
need those things, though, unless you want to freeze and risk frostbite! I'm not joking, take a look at this video from Kagura posted this year: https://www.youtube.com/watch?v=2cnGJcARXn4
Those are the general conditions of the Yuzawa area this time of year. You will fall. A lot. Your hands take a lot of the brunt, so you'll need gloves for sure. Snow will get on your head and be very cold, so I wouldn't go without a hat either. I would also absolutely get goggles, but they're the one thing that you could manage without only because as a beginner I doubt you'll be getting up to enough speed to need them... but if you did, the snow becomes little ice shards in your eyes and you wont be able to see without them. Tomorrow the weather forecast says it will be sunny in the morning changing to snow in the afternoon. So if you go past the morning, as the conditions change I think you'll want them. By the way, when it's sunny the glare off the white snow is intense... it can even cause sunburn! So even in the sun I'd recommend the goggles and hat.
If you don't have them, you can probably buy them there. Most of these places have a shop selling the basics for people who forgot/don't have them. Bring cash (I'd bring at least 10000 minimum), as some of those types of places don't take credit card! I don't know about Kagura specifically though. I also want to know do I need to buy the Ropeway and Gondola ticket?
The one day lift ticket from Kagura includes everything except (I think) the Naeba Dragondola (which isn't open anyway), as that is the connection to Naeba so you need the double park tickets for that. You'll want to buy the Kagura only lift ticket for 4900 yen, and then can ride anything at the park.
By the way, I hope you don't take offense at this, but you don't seem at all prepared for just how cold it's going to be in Yuzawa. I would recommend planning to get the appropriate gear when you get there, and also reading through this: https://www.healthline.com/health/frostbite-stages
Frostbite can be dangerous, and happen faster than you might realize! If you can find kairo, they are warm little packet you can put in your pockets, between your socks and boots, and even stick on your body (don't go right next to the skin!) I always stuck some in my boots and gloves when snowboarding, as I get colder than others seem to.