Affiliate Competition

also, can anyone recommend the best SEO course for a wordpress site?

Any decent niche is going to have competition so it doesn't matter.

Are you talking specifically about higher volume keywords or product specific keywords?

Competition is a good thing, especially online.

If you only see a small group of marketers it could be a good thing, or a bad thing.

It might not be profitable, or it might just be overlooked. Only one way to find out for yourself, and that's to create a site of your own and test it out.

And it sounds, from all your questions here, as if you're looking at them from the perspective of search-engine traffic?

Please excuse the observation that, for myself, it's about the last thing I'd ever look at, in niche selection.

Only you can decide this.

To me, it wouldn't be in any way relevant. I wouldn't care if the entire front page comprised exclusively review sites, or if there were none.

"How many of them there are", even if your perspective is a solely-SEO-oriented one because you have no aspirations of getting any better traffic than that, doesn't tell you what you need to know, anyway: even within a strictly SEO context, "numbers of competitors" doesn't mean a thing - what matters is whether you can beat them in the SERP's. And that (like almost all the other success-determining factors in internet marketing) relates to quality, not to quantity: you can hardly predict it from "how many of them there are"!

For which keyword would you rather compete: one for which nobody else has a "review site" but the whole of the front page is filled with age-old, high-quality authority sites, or one for which there are 1,000 "review sites" all of which are the typical affiliate review-site kind, which any sort of respectable SEO based on quality backlinks from relevant sites will very quickly trounce?

If you're looking at SEO traffic, for some reason, you're not competing just with "other review sites", are you? You're competing with other SERP's listings for your keywords as well. Even - to some extent - in the case of traffic actively looking for a review site.

You have, effectively, 3 or 4 competitors. If you can't get your site among the top 3-4 rankings for a keyword, that keyword's probably not much use to you. It doesn't matter whether the competing sites are "review sites", does it? Nor does it matter whether they're the top 3-4 listings of 10,000 SERP's listings or 10,000,000 SERP's listings for the keyword: the top handful are your competitors, regardless of the total number, site-types and so on. Either you can beat them, or you shouldn't be playing that game.

Maybe you shouldn't be playing that game anyway?

I advise you not to depend on search-engine traffic. Non-SEO traffic is a good way to get more than just an "edge" over competitors. Its overall quality tends to be so superior to that of Google traffic that it can even be a way of forgetting "competitors" altogether. I don't like to put time and effort into trying to attract "organic SERP's" traffic, for two main reasons. First, it's very precarious and makes your business Google-dependent, and any business that's Google-dependent is no more than one algorithm-change away from a potential accident (or even a potential disaster), as so many Warriors have been finding out over the last year or two, some of them to their very great cost. Secondly, for me, search engine traffic has been uniformly the worst-converting traffic out of everything I've ever tried in 8 entirely different niches over the whole of the last 4 years - search engine visitors to all my websites typically stay the least time, view the fewest pages, opt in the least often and actually buy anything by far the least often. I admit I do get tons of search engine traffic to all my main sites (because high rankings for multiple keywords happen to be a minor side-benefit of the main targeted traffic-generation method I use to build my business) but I'd certainly hate to have to make a living just from that traffic, or to make specific plans to try to increase the flow of that sort of traffic. I prefer almost any other traffic-source.

Nothing is impossible, and a tiny minority of people succeed with them, but - statistically - review sites are a very, very difficult way to set up a business aimed at deriving income from affiliate marketing. They're just "not, overall, what they were, a few years ago". My apologies for surrounding disparaging, but everything you've said suggests that - at least to some extent - you're stacking the deck against yourself, here - and someone needs to tell you that.

Again, something I wouldn't touch.

The joy of affiliate marketing is that - unlike vendors - we can build up real, asset-based businesses without being dependent on the contintuity, success and availability of any specific, individual product at all. Why throw that mega-advantage away?

Well, SEO is not the only way to get traffic to your site. There are a a ton of other ways, like youtube, social media, paid traffic etc, which are more reliable than the search engine traffic. Don't depend on a single traffic source.

That said, don't worry about a little competition. If you diversify your traffic enough, you can find ways to get traffic to any niche, regardless of the competition.

There's a million different variables really.

Variables establishing keyword competition is so vast that you haven't really provided enough information required to determine whether or not you can rank.

The best advice I can give you, is to not rely solely upon SEO, and instead create content that you can share alternate methods.

Social sharing, email marketing, article dissemination, etc.

SEO is a good backup plan.

Just my $.02

You does not need to find any niche which does not have any review. There are thousands of review for one product within the whole web. Just you will have to target your audience and reach your products towards them.