I would run with what you have on to start, if they have been on the car for a while its a good base comparrison to start, a sessions day is a good first event, as you dont get time to get carried away (15 or 20 minute sessions). If they are too worn then AD08, RSR are good fast road tyres which will get you through your first trackdays, or any premium tyre like the RE070 etc, it just depends on your driving, confidence etc. You will never reach the limit of the DC5 on the road, you might reach your limit though! Running a tyre similar to your level on track is good as it wont hide your mistakes and you will learn more in my experience.
Track tyre pressures are down to the individual, suspension/brake setup, track and conditions, its a case of experimenting until you find what works for you and the tyre you use that day. On a dry day with any tyre you could start with 26psi and work up from there, certain tracks will be more punishing on one side and you can adjust to compensate, or just use the pressures you run on the road, but keep it simple to start so you can notice the difference, you dont want to be worrying about too much on the day, just keep monitoring them at each session.