Yoast is good. It's all you really need to use for the on-page optimization. The next thing to look at is your site's speed performance. Make sure you use caching, consider using a CDN, etc. to boost speed because that's becoming more and more important to Google. Especially look at your TTFB speed as that can get you penalized if it's too slow.
Once you've done all that, it's link building time. To compete you need a solid backlink profile with new links getting built all the time. You can nab some regular links through forum posting and whatnot, but to get the real money keywords you'll need even more than that. You'll need some higher profile websites to link back to your site and that's the hard part. There are ways to get these links naturally, but it's a lot of time and work involved. Or, you can take the quick route and buy such links. Just be careful not to buy too many spammy links and get in trouble. A couple really high-quality links are much better than 10,000 crap ones.
Another suggestion specific to your site is that you need to get rid of the /wp/ on your root domain. Google gives a boost to root domains over other pages on the site. However, your homepage appears to be a subpage because of this URL. I'd use some URL re-writing rules to hide the /wp folder in the URL. You'll probably see an immediate boost just from that.