Welcome! You will learn a lot here!
1. I wouldn't reccomened, sandpaper perches for your finches, the sandpaper is too harsh and can cause sores on the bottoms of their feet. I personally use natural branches, a little rough so they can keep their nails and beaks in check themselves. Occasionally, it may be needed to trim their nails yourself, but you can easily doe that with a pair of baby nail clippers and some good lighting.
2. Gravel, I feel is essential for them. It does help to digest food and is a good form of calcium and minerals for them. I get mine from a local bird farm and I know they use theirs for all of their birds.
3. I know some leave their wire grate in the bottom of their cage and have no problems, and then I have heard that sometimes there are incidents where the bird may get his leg hung up and that could be detrimental to them. I personally have the grate in mine because it is non-re moveable, BUT, I lay my newspaper on top of it so I don't run the risk of any leg injuries. A second concern, of no grate, is them eating seed on the bottom of cage as well as droppings, so you will need to make sure you keep up on the paper at the bottom. Most of us change the paper out everyday or every other to keep on top of this. Eating droppings could mean illness.
4. Also, you will want to make sure you have your birds in a room with sufficient lighting so they can regulate their days and nights according to sunrise and sunset, as well as seasons. If you choose ( not necessary unless as long as they have suffiecnt light) to put a light on their cage, make sure it is a full spectrum light and you can read more about that here:
http://www.finchniche.com/features_light.php
They also benefit from fruits and vegetables but be careful which your choose, some can make them sick.
Here is some info on that:
http://www.petuniversity.com/birds/cana ... inches.htm
I'm sure long time finch fanciers will come along and give you their two cents and advise. There is a ton of it. Enjoy your birds!!!
