Hey please do not pay for the links. Paid links are not useful and they can cost you harm. Its better to have the organic linking instead of the paid linking as the sites which provide the paid linking mostly does linking in the black hat way that can harm your site and google can also put penality on your site. Its better to have the link building manually done. Although it can take time but you will have the results that will stay for long time.
Ofcourse organic linking is more good than paid linking because paid linking stays for the time you have paid for the site to promote but organic linking is done free and it totally depend on your work and content.