I obviously don’t know what your project is but I suspect, given how you successfully utilize different people for different tasks, you should apply this approach to SEO too. To begin, I would suggest you get a really good idea about what SEO is, how it works, different approaches, ideas, concepts etc. There is a lot of info out there and available for free but obviously there is a lot of rubbish too - I suggest that you stick to guides that are from major SEO tools, Google etc and not just whatever comes up in searches.
Personally, for a beginner/great introduction and overview, I would recommend this post and series from Moz who are one of the leading SEO tools around. If you have heard of Domain Authority (DA) and Page Authority (PA) - these guys invented that metric for measuring sites and pages.
While the vast majority of SEO on Fiverr is link building related, this is just one aspect of SEO - there are thousands of potential factors! I know you use good writers so that is an exceptionally good place to start. On site SEO (your site, content etc - basically everything you can control on your site) is the foundation for success which off-site SEO (like link building) can then build on.
Anyway, drop me an inbox message and I will send you a couple of advice leaflets I have written which will help you do a lot of your own SEO.
PS. @writer99025 to paraphrase Winston Churchill:
Tomorrow I can shave off my beard and I will look younger, while you my dear, you will still BE older.