It is great that you pay attention to the quality of the image and the sound of your stream, and there are cheap and expensive ways to improve the way your feed looks. If you are a new model I recommend taking care of the things you can do for free or for cheap I do not recommend buying expensive equipment until you know for sure this is profitable for you and something you want to be doing for a long time. Otherwise you might end up spending a lot of money and not recouping the costs. Ideally you should be improving the quality of your stream as you go along reinvesting some of your earnings in this. Once you are past the regular quality, sound and lighting are not things that will make or break you so you should focus on finding the right type of show, interaction, strategy and persona first.
Expensive essentials are a professional webcam and a solid internet connection. Extras that are free or cheap are an ethernet cable and OBS. Everything else you can pick up in time. I suggest about 6 months of camming to be sure this is for you before splurging in other expensive equipment.
That said, I use a Røde external mic for the sound. I play music directly from my computer through OBS. The rest of the stuff I use are all in my model Cheatsheet you can find it here:
http://milamcfly.com/hkjgjhftd54fhhg/cheatsheet.html
There are tons of ideas in there but like I said... spend in moderation for now.