Which is the best website for group buy SEO tools?

Sorry I am not too sure what you mean by a platform to buy these tools. If you want ahref, semrush or moz then you just visit these sites and subscribe to them. There is no magic platform to gain access to these services. 

However, as you also say you are new to SEO, then it's more than possible these tools may be beyond your understanding to get much out of them.

There are many free tools out there to get you started, but a lot will depend on what you're trying to achieve. For example, screamingfrog offer you a free version of their site crawling software (up to 500 pages), Google Chrome offers you an audit by pressing F12, GTmetrix offers you a technical breakdown of your site,  Ubersuggest offers you a free audit, Google search console shows you how your site is being found plus much more.  

As you can see there are many options and a lot I have not mentioned but in order to know which tools you require will depend on what you're trying to measure / achieve. 

SEMRush is my tool of choice. Its really good. Also I would advise you to look into the Blue print training as there are a lot of good tolls available from there. Another very worthy mention is Hannah Rampton - she makes some awesome Google sheets and docs that go with Google products.

If you are just starting out - familiarize your self with Google Search Console and Google Analytics.

This Pdf contains all the SEO essential tools in one package.

And also this pdf tells you, how efficiently you can use those tools for the website. 

It works for all kinds of niche.

This guide provides

How to Drive Traffic

Keyword Research Tools

Web Analytics Tools

On-page & Off-page Optimization mistakes

https://www.dmshelter.com/items/detail/489/Make-your-website-No-1-in-SERP-SEO-Ranking-Research-Tools

You buy Ahrefs from Ahrefs, you buy SemRush from Semrush. You don't buy them from a third party together.

Personally, Ahrefs always wins in my eyes. BUT, as you can see by other replies, this is purely based on my opinion. The two biggies for "all-rounders" tend to be SEMrush vs Ahrefs.

outdoorsumo.com

Semrush is what we are using, but before I used also keywordtool.io

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there are so many tools for SEO. we call them Atomization tools. BUT if you will use the Tools for SEO. this will damage your website Score and Content. it creates the problem about the speed of the website and brakes the Links. better you will prefer the SEO Manually . in this way I will recommend you for SEO Manually. if you need any kind of Help. contact with me.

I'm search it too, because sometimes it always says error

I Personally use Flikover.com . They have a many useful tools including SEMRUSH,AHREFS,Spyfu etc.