How to select a sub-niche within a niche

My domain is <snip>Link deleted</snip> and after listening to Adam Short I got trade forex on my domain. So I thought I use this keyword to my advantage.

Little did I know it has high competition with only 368000 global searches and 60500 local search for US. lets see for Singapore at least that is my target.
only 4400 searches.

My question is should I do SEO for a high competition keyword on my articles and title header or
Should I look for low competition and do a keyword density on my articles as well as header?

Low competition keyword relevancy is only down to the following
“How to Trade” 45 million global searches and Singapore 246 million searches.

or should I focus on this
“Currency Trading from home” with less competition but only 320 global searches and less then 10 from Singapore.

Keyword Use
I’m looking at currency trading but these as no relation to my domain which start off with tradeforex so should i use trade forex as my base keyword instead?
But this is what google have to say

Keyword - Trade Forex
Competition - high
Global Searches - 368 000
Local Searches - 4400 (Singapore)
CPC - $19.86

Keyword - How to Trade
Competition - low
Global Searches - 45 million
Local Searches - 246 000 (Singapore)
CPC - $4.60

Keyword - Currency Trading from Home
Competition - low
Global Searches - 320
Local Searches - less then 10 (Singapore)
CPC - $0.13

Keyword - How to do Trading / How to do the Trading
Competition - low
Global Searches - 90 500
Local Searches - 880 (Singapore)
CPC - $0.13

By the way how many keywords should we target? My Niche is Forex and sub niche would be a breakdown of type of trading or currency pair to trade or trading strategies am I true?

Audience: Maybe Singaporeans then later US market.

Right not my article range from beginners to psychological aspect of trading and I am not getting any eyeballs for it.
So my question is where did I go wrong from keyword point of view.

Warm Regards

David Aw