I've used Fiverr for some logos for pages and such, for that it is fine. One guy on there did an analysis of a local site for me and sent a report with recommendations. That worked out OK too. I figured for $5, what have I got to lose?
I would stay away from the SEO stuff, for the most part. ESPECIALLY the 1,000 links for $5 stuff - it could end up doing more harm than good.
Maybe I'm wrong, but I feel that SEO in general is a waste of time. Making sure your pages are SEO friendly is a good idea and making sure your website meets basic standards is smart too.
But trying to buy your way to the top of Google with links, Facebook likes and stuff like that... I'm just not convinced that it works. EVERYONE wants to be on the first page of Google results, but there are only so many slots. So, if you are selling anything that is popular, it would be incredibly difficult to do. Of course, if you specialize in selling "Patagonian Donkey Balls" then go for it. In that case, you might not even NEED SEO!
I never did much with SEO on my main site. I built my traffic slowly and over time. I included a flyer with a coupon with each eBay and Amazon order. It does not cost much and a certain percentage of people will turn into regular buyers. I have started to use, thanks to Aspkin's advice, Adwords which are highly targeted and so far, so good. My site does about $6,000 per month in gross sales (NOT PROFITS) and that is not bad.
I think it makes more sense for most people to stop thinking in terms of keywords, articles, links and other such things and START thinking about their Return on Investment (ROI) on paid advertising. That could be including a flyer with your eBay orders, Google Adwords, an affiliate program, or other things like that.
Years ago, you probably COULD hire an expert and get on the first page of Google. You could also BUY your way in to Yahoo. Those days are over, the web is too big now.
When you think of all the SEO going on, and the fact that there are what - 20 results on a Google page? - you quickly realize that a ton of money is being spent on SEO and the results have to be disappointing for most people.
Six Figure Boss is a good place to start, it discusses many potential advertising methods. Personally, I like the idea of affiliate marketing because you know in advance what percentage you will pay on each sale. But Adwords works too. And the BEST way of advertising is to your current customers on eBay and Amazon - you know they are interested in what you are selling. Give them a reason to come back to you and they will. Give them a discount instead of paying a commission to eBay. Offer great customer service. Keep them engaged with a monthly newsletter sent via email.
This is just my opinion based on my personal experiences. Aspkin and others are more experienced with this than I am. They might have better ideas. I thought I'd throw in my 2 cents.