To get into some sort of racing or Club Sprints with your car you need to join a CAMS Affliated Car Club around $100-. From there you need to purchase a CAMS Licence Level 2 for $80- odd. Then you can go on or attend any Club Sprint Days not just Nissan ones. Many Clubs welcome along cars of any make or model. Cost for a track day depends but is around $120- for the day. that generally gets you 4 to 4 outings onto the track with 3-4 hot laps.
then the cost of tyres, petrol, car problems and trying to better your times and going faster. $1,000-s. You get my drift. What state are you in?