Some fantastic advice here already, but I want to emphasize a few points:
Start small, especially if you have a big property. Changing the entire landscape will be a process, so start with a small area that you can actively maintain and then expand from there. Once your plants are established, they will take much less maintenance than when they're first getting going.
Starting from seed can be an easy way to propagate uncommon plants you find around you (and a great way to preserve local genetics for native species), and it can be very fun and rewarding, but it's not necessarily the easiest way to start. I might try a mix of strategies to see what works best for you. Try starting a few things from seed, and also buying a few perennials in pots from local nurseries. Keep in mind that a lot of plant seeds won't survive desiccation the way domesticated crop seeds do. You can find propagation information online that is specific to the species you want to grow.
If you do plant any trees, make sure to place them thoughtfully relative to permanent infrastructure like sidewalks, structures, or pipes. But If you have space for them, larger trees are exponentially more valuable for urban wildlife/biodiversity than smaller ones. And they don't need as much room at ground level as many people think. In general, oaks are probably a keystone species in most of the Eastern US, and there are many species, so there should be one for almost every environment. I'm an arborist, so let me know if you need more specific advice on the tree stuff!