12 months and $300/mo to improve my credit

Whats up folks? I am looking to buy my first piece of real estate in about a year. I expect my largest obstacle will be my credit score. I am starting at a 600 and working hard to clean it up. A snapshot of my current position is below. What I would like to know is where do you think I should be contributing my extra money? I have some BAD debts I could eliminate, some debts I could work on, add to savings, or do something else? Any advice is greatly appreciated.

• I am currently slowly paying down a $2400 balance on a $3000 credit card. I was recently denied a credit line increase.
• I recently got an unsolicited credit line increase on a store card. 
• Also signed up for a SelfLender account to build positive history. Its just a credit builder secured loan.
• I have a car note that is current.
• I have unpaid rent and fees from 2012 of about $2k.
• I am making payments on the last two years of taxes. About $4k on those.
• I have not yet started on my student loans which will be $380 a month. Not eligible for any repair programs: they will go through a consolidation after 3 months.
• I could get a secured credit card.

Just to add more clarity around the goal, I am aiming to get an FHA loan to buy a du/tri/quad plex.