If you're looking for high-authority backlinks for your niche site, Serpzilla is a good all-in-one link building tool. It offers a variety of link types, including niche edits, guest posts and contextual backlinks, and uses machine learning to evaluate and select high-quality donor sites. Serpzilla guarantees 100% Google penalty-safe backlinks and offers automated backlink placement, a centralized dashboard and multiple subscription plans, so it's good for users at any level.
Another option is Ahrefs, an all-in-one SEO tool that gives you access to a lot of data to help you climb search engine rankings. It includes tools like Site Explorer for backlink analysis and Keywords Explorer for finding the right keywords. Ahrefs also offers a broad range of subscription plans, so you should be able to find one that works for you.
Last, LinkSafari offers an AI-based link building service to find, manage and optimize backlinks. It includes tools like Get Backlinks to find new opportunities and Manage Backlinks to track and optimize. With three pricing plans, including a free option, LinkSafari is a relatively inexpensive way to improve your link building.