As @theedpope stated, take it slow, get it right and work in a logical pattern . . . in regards to exciting things you can do the world is pretty much your oyster, your not going to find a more open and community/hacker supported HA system than this anytime soon
Welcome. I started because I wanted to be sure my Garage Door was closed. So I bought a hub and a garage door controller, programmed SmartThings to let me know if I left it open and was very happy with the result.
Then I added some switches mostly to try them out and some motion sensors. I use the sensors to track my Dogs movement and I have a camera to watch them when they are “in action” LOL
The Amazon released the Echo and things got really fun. I added IR senders to control my Split AC system and now when I feel too hot I simple say “Alexa turn on AC cool”, that really won over the Wife Now I can voice control my lights and my ac/heat. Gotta love that !
It’s a lot of fun and frustrating as heck sometimes but as others have said you will enjoy the company of many peers that love hacking around with this thing !!! We are in a growing pain stage as the V2 Hub and many other changes have been implemented all at once. So you may struggle a little at first but I am optimistic that things will be much better once the dust settles.