In need of advise to quickly boost up my credit?

Happy New Year to all,
Can someone please give me advice on how I can quickly improve my credit.
This is my sad current situation where I can’t get any credit at all. Which negative account should I get rid of first.
Credit Score (Expedia): 606
5 Negative Accounts:
– Citi Cards: Opened 4/2003, Closed, Balance:$ 7,713. I am paying as agreed on time.
– FIA Card Services: Opened 5/2007, Closed, Balance:$ 3,301. I am paying as agreed on time.
– Wyndham Vacations: Opened 7/2005, timeshare was in 2009 repossessed, Balance:$ 6,453. I am not paying this account.
-Chase Card: Opened 10/2007, Closed (Charged off), Balance:$ 2,424. I am making timely payments to a Law Firm however Chase is reporting payments late. I disputed this with 3 credit bureau with no luck.
1 credit card in good standing:
-Capital One: Opened 7/2011, Open, Balance $ 300.
Guys I make decent money and I can payoff the chase card by next month. The reason why I opened the Capital One card was to start building my credit again since my old cards are all closed? Should i try to open another credit card or just stick to that one?

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