If there's one thing that's an essential resource of Animal Crossing: New Horizons, it's wood. The majority of the things you will be able to build, can't be done without some good old wood. You can use an axe to smack some trees and grab wood that way (just watch out for bees).
Now, bear in mind that there are different types of wood you can collect. Each one has its own color and name such as dark wood. There are others too. It's like this because certain items you want to create, need different styles of wood.
You'll get a recipe book that will tell you what certain items require such as furniture. Some things just take certain types of wood and they randomly appear when you hit trees, so there's no specific area to grab the wood. The good thing is that you'll see a fair balance of all kinds, so you should be OK. You just need to be wary of your inventory space.
Dig For Items
What's one of the first things you think of when you think of uninhabited islands? Buried treasure, right? Well, in Animal Crossing: New Horizons, you will be able to go digging for some goods. You'll need to craft a shovel which you can do by using the recipe book we talked about earlier.
Once you have the shovel, start digging at random spots. You never know what you might find. One of the best things you can find is a bag of Bells. Bells are the game's currency and can be used to buy many cool apparel and furniture items among other things, with some of them being limited time.
You can also use the Bells to pay off your house. Yes, you need to pay for your crib in New Horizons. You can pay it off gradually to Tom Nook. But you can also find cool items such as fossils, which have a neat purpose once you progress a bit in the game. The fossils can also be put on display at your house.
Customize Your Own T-Shirt
One of the really cool, smaller features in Animal Crossing: New Horizons is the ability to design your own t-shirt. This feature should be available to you very early, so you can go ahead and customize it to your liking in the designer.
It'll take a little practice, but you can get pretty comfortable with it fairly quickly. You can really get creative with how you want it to look. It'll take more time if you're trying to design something more complex, like a sports team logo for example.
I designed a shirt with the Chicago White Sox' alternate logo on it, but that was mostly just text-oriented, so as you can imagine, that was fairly easy to do. This is something you can try too. Maybe start out with something more text-based. If you want to try to create something bigger right away, then go ahead and let the creativity flow and just have fun.