methods for various keywords?

So ive been so focused on my top 10 keywords for almost 2 years I gave no attention to longtail and low searched keywords. Add all these up and I got something really nice.

Can you suggest some methods that I and others can use to get these various keywords to rank?

What have you been doing to rank your top 10? Same principals. Link pyramids, on page SEO, quality backlinks et all. Usually the longtails don't take near the work.

ugh.. but I gathered a list of like 500 keywords.

that would take 50x the resources /time/ money that I spent on my top 10

I am not sure if I am understanding you question but this is my experience. I have had my website for 7 years and I learned that having too many keywords was hurting me.
For backlinks I have tightened the number of keywords. I use: Doctor Who Companion, Doctor Who BBCAmerica, Doctor Who Actors, Doctor Who 50 like that instead of listing each and every actor as a keyword.
When I write a post and add keywords I try to think of what question would a person ask Google if they were looking for my article. I use those in my title as well. If the article is about Jenna-Louise Coleman my keywords would be less broad and article specific. Jenna-Louise Coleman,Who replaced Amy Pond,Who is Clara Oswald,Who is Jenna-Louise Coleman dating,Jenna-Louise Coleman children
I hope this what you meant.

Ive focused on my top 10 keywords for 2 years. I have a list of 500 keywords that are in my google webmaster tools. I would like to start focusing on them but I just dont know how to focus on keywords that arent high ROI. Ive spent a nice amount of money to rank my top 10 and its worth it because my ROI is great. I dont know how to do it for the low quality keywords.