Rebuilding credit quickly

I have a very bad credit - fall mostly from a few years and some bad things started now. (Includes judgments from 2002)
In recent years, I have to believe that I pay everything on time and I start to rebuild. I have a target card (already for about 1 year) and car loans (about 2 years - will be repaid in 8 months) and MasterCard partially guaranteed (1 year) this account was never late again. Everything before that is negative.
The MasterCard that I have a very high interest rates - the cost of maintenance and annual fees and costs $ 5 to me also only afford to pay. I added recently and closed the account because the cost is too high to have the small advantage to warrant reported my credit card ($ 375 limit)
My Experian score is 498 now, which is significantly less than 2 other numbers, but I understand that there is most often used by creditors.
My credit is bad, because I never thought that it was important when I was young and I do not care. have now stabilized financially I am in an attempt for the first time in my life frustrated, I pay everything on time and my rating is not higher than ever.
I know my value by the fact that the loan I have a very small credit line and sometimes I max them out and pay only the minimum payment (not always - I have to pay sometimes much more) is characterized I just hope that my guests get some of the fact that I had paid everything that was agreed upon.
My question is what to increase the best way for me to get my speed value. It is not good enough to get a new loan at this time. I closed an account cc and now I will pay the store target card still open (and not use it) Does this help?
Since I can not get new loans now I do not know what I can do. Ideally I would like to get a credit card without the cost of building crazy and use it sparingly - just enough for a positive report on my report - but I can not justify payment of fees by type of card that I received FDA approval.
Is my only option to continue to pay my car and Target cards on time and wait just go to my grades until the end? If I go this route, how long does it take to increase my score significantly (without any new loans)? Thank you for your contribution!