Building a solid domain portfolio is not a piece of cake; it may take you several months or years to achieve this goal but it will definitely be worth it in the end. When you are in the fishing phase, look at the potential of the domain name. Another common strategy used by seasoned domain flippers is to get hold of some high profile domain names and sit on them until they soar in terms of value.
  Since starting SEO back in 2009, it has become very difficult to rank brand new domains. Unless you are building a brand, it's highly recommended that you start every new money site with an expired domain. Additionally, if you're building a PBN, you should only consider using expired domains. The problem is good domains start at $50 a piece, and anyone charging less is either full of sh*t or selling garbage domains, and I mean that. If it sounds too good to be true, it probably is. DomCop has a great offer that all of you buying expired domains should consider. For the price of a couple domain names, you can use DomCop for a month, snag some excellent domain names, which would otherwise cost you thousands of dollars. If you're considering expired domain software and don't have the knowledge to program your own crawler, I'd lean towards DomCop.   
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.