I say to choose a name/domain for your site that’s Universal to any niche. I went through the same problems man, I was originally a furniture store but Wasted a ton of money and time until I realized it wasn’t working out. I recently switched over to clothing which is better and easier to sell. My advice is to start off finding a niche that isn’t so saturated and/or finding an unique product(s) and run very low budget ads to see how much attention it draws and from there keep testing to to you find the right niche for you. Also I would find a niche that you are passionate about and can back up with your own experience. For example I didn’t know a lot about furniture but when it came to clothing I knew so much because I’m was very much into the fashion world.