If there are other cats or dogs in the home, they can be a little tricky to give different individuals different types of food and ensure that they do not manage to access each other. A tip for solving it all is a food bowl with a lid that is only opened for the right individual. See more here: Surefeed Feeder
Maine coons like to stay outside a lot, so harness & leash are good to get early to get used to. But remember that they grow incredibly much the first 2 years, so expect that the harness will quickly become too small!
When buying a transport cage, remember how your cat will look, a small ordinary transport cage for cats often becomes too small. One cage we can recommend at a really good price is this: Pet Transport Bag Pet Club
If you plan to have the cat loose outdoors, we recommend that this only happens after a couple of months that the cat has lived with you, so it really knows where its home is. We also recommend that the cat has GPS so that you can safely see from your mobile phone where the cat is.
An appreciated GPS we can recommend is this: Tractive GPS