Buy a SA not MA Helmet. This will save you the cost of having to buy one when you start road racing.
Start with driving schools for Autocross. Very cheap and applicable to what you are currently doing. From there look at the other types of racing and find an school that will specialize in that area.
Solo 2 is a great place to start. But don't be fooled into believing it is cheap if you are chasing a National title. I spent $7,000 on my S2000 when I was in AS chasing one. In the Mini I added Koni shocks at $1,800 and I amlooking for light weight wheels probably about $1,200. Don't forget the fresh rubber for National events at $1,000.
Find a car that is as close to what you will want for a race car. It is much cheaper to buy something finished or almost finish than to start from dirt. Staring from dirt is very expensive. You get the honor of buying all the parts new or searching for used parts.
Track days are great. Apex Driving Academy is one of the best deals around. Safe group and good instructors. This will give you a feel for the different tracks before you join. Get signed off solo by one of the DE groups before you join a track. I know ECR will offer lessons to help you solo if you are a member.
Look at SCCA and NASA as two possible groups for road racing.