I’d be careful where SEO is concerned. Bad backlinks/spammy directories/paid links/copied content etc. are all more likely to get you penalised and blacklisted rather than boosted and this is the kind of thing you’ll find on the cheap on sites like Fiverr.
Search engines have come a long way and the best way to rank is simply to build a great site that people organically share. Other than best practices and good HTML there are no shortcuts.
I am a fan of Ubersuggest (app.neilpatel.com) which you log in with your Google account (assuming you have your site setup on search console) and it will analyse your site, give you tips, content ideas and best of all show you what you currently rank for and help you track keywords over time so you can watch your efforts improve your position.
The Fiverr gigs that promise X amount of traffic is almost always useless bot traffic that only serves to waste bandwidth.
That’s not to say everything on Fiverr is bad. I both buy and sell on there frequently with success but where SEO and traffic is concerned it can be a minefield.