I've been using Home Assistant for a few years now. It's hard to give advice without being specific, I will say it's very daunting at first, it will take months of setting up and tinkering to get things right, but it is almost limitless as to what you can do with it.
The best advice I can offer for Home Assistant is to have some sort of end goal, what do you want to integrate, what automations do you want etc. One of my goals with Home Assistant was to have everything controlled locally and not having to rely on any cloud services, as well as having automated lights around the house depending on time, motion sensors and door contacts.
A good place to look is the Home Assistant subreddit for some good ideas and just a view of the possibilities. If you're after automation of lights then choose a system to use such as Philips Hue, then you can add that as a HA integration and start setting up automations. If you want smart switches, buttons, sensors etc then look into anything that's Zigbee or Zwave compatible and you can also connect them directly to HA.