I'd like to know how long does take you to get rank number #1 on Google search results. what factors should I focus on SEO for better rankings?
In addition to what Nytshade said, which was good advice, it also depends on what type of content you are trying to get ranked where, examples: informational blog post in regular Google search, local business in Google places, image in Google image search, YouTube video, commercial product search in regular Google search results, etc.)
And it depends on what you are competing against. If the competition is strong (excellent on-page metrics combined with lots of domain authority and page authority because of powerful inbound links) then you will find the task more difficult.
And it could depend on what tactics you are willing to use (like whether you are okay with buying links, building link farms, buying other domains, etc. and risking a penalty or not).
If you were trying to compete against a really strong page and you were trying to do that with a brand new website, then it could take you a really long time (years potentially unless you were willing to buy links, redirect link juice from elsewhere or take some other kind of penalty risk).
If you have a blog that has a lot of domain authority and constant Googlebot traffic (and you are competing against sites with less domain authority than you) then you can get a new post ranked for a keyword in a matter of minutes (like as little as 2 minutes sometimes).
There are many variables that come into play. To get a more accurate idea of how long it would take, you would need to provide a specific scenario.
Here is an excellent tutorial for getting something like a blog post ranked number one on Google. Getting a local business ranked number one in Google places takes additional things into account.