You can add it as part of a private blog network or you can 301 redirect an expired domain to your site to bring some trust and authority to your site. Now, in my experience, the best place to look for expired domains is this free website called expireddomains.net. So, you just have to head over there, make a free account and this is the page that you’ll see when you log in.
That said, my recommended budget for beginners would be $500+. Using this budget you could buy a bunch of high-potential $10 domain names, expired/dropped domain names or a mix of both. It’s very important to invest only what you can afford to lose and treat this as a side hustle till you get the momentum going. As you gain experience, industry expertise and some sales under your belt, you can then consider slowly growing your business into a full-time gig.