firstly start with groups of keywords that are doable
unique content around the keywords - good title and meta description and then drop your keywords sparingly into H1 and alt tags
bold a keyword will also help - then you need to create links, slow to start and then build them up gradually
better if you optimize your webpages first. then go for off page. most of the people go for mass back-links. but remember that google also are so optimized so you cant make it food go natural way, you will win the race
what’s your website? The most important thing is that you optimize the title, descriptions and keyword tags to start. Do you have original contents and how often do you add them? Website optimization is not a one-step deal.