1. There is no undiscovered magical formula of keywords. Whatever keywords you can think of be very sure, amongst the billions of other websites, that someone already beat you to it.
2. Google gave up paying attention to meta data <head></head> stuffed keywords long ago and the growing trend is not even to include them as meta data.
3. Unless you're in a specialist niche topic such as 'Why mice get toothache', you are not going to get on page one of google and beat the world competitors with marketing budgets of millions.
You have two opportunities to draw readers to your site. Without these two you don't exist, so spend time on them and get it right.
The first is your site title and the second, the serps description. Both of these are visible to readers and will determine whether it's what people are searching for and click on your site, or not.
Let's give an example (off the top of my head)
1. You sell shoes, specifically sports shoes, they're cheap and you're based in Oregon.
2. Training shoes, running shoes (sports shoes).
3. They're a bargain, affordable, cheap (discounted).
Your keywords are 'discounted sports shoes', either singly or in combination. Those three words can also be your brand name, or form part of it.
Your site title 'Discounted sport shoes in Portland, Oregon'.
Your page title <h1>Quality sports shoes at discounted prices</h1>
Meta description 'We are specialist providers of bargain price sports shoes in Portland, Oregon. Contact us for a catalogue of brand name quality sports footwear at discounted prices.'
Your 'secondary keywords' would be running shoes, training shoes, quality sports shoes, bargain price sports footwear ... Liberally sprinkle these key words throughout your landing page in a natural sounding way.
'We are able to offer discounted quality sports shoes direct from the manufacturer ...'
You can probably do better if you spend time on it, but you get the idea?
Finally, remember it's a buyers market. There is no single SEO way to guarantee your site be successful and if it's failing, don't be afraid to experiment and change the h1 page and/or description tag.