What a great name! I'm so glad to hear you are getting a bigger tank, goldfish need at least 10 gallons each so the bigger the better. Plenty of room for her to have a friend too.
Now I am wondering if you know about the nitrogen cycle? It is one of the most important things to know about when you are a fish owner. Please have a look up about it on the net and in some books. If you have any questions about just ask away, it took me a bit to get my head around it but I'm so glad I know about it.
Any plants are good for goldfish tanks generally. I like to get a mix of soft and hard leaved ones because the fish will nibble (and most likely destroy) the softer ones and the hard leaves one can be left there for decoration and to do their magic
You get some staple pellet food sinkable or floating, frozen foods such as blood worms and brine shrimp, freeze dried food, you can feed them fresh vegetables and fruits, frozen peas which you just deforst and deshell and mush up a bit and toothless will love it. Pretty much any other special fish treats you can find. For example mine love algae wafers intended for sucker type fish. There is a couple of posts on here about foods for goldfish which are incredibly detailed so have a look around.
Make sure you get a good filter, some beneficial bacteria, a water testing kit, air stone and air pump, water conditioner and maybe some decorations for your tank but nothing to small which they could get stuck in and hurt themselves.
We all love to help here so I hope I have
If you have any more questions just ask away.