As I currently own a S2000 and I'm looking at a 350z I will throw my experience out there.
I have a 2004 S2000 with Goodyear tyres and ferodo ds2500 pads all round. I have done bedford, oulton park and 1 autosolo this year.
Each track day has not killed the tyres but taken the life out of them, so they are replaced not long afterwards. A set of around £450 and they are 17's.
A track day costs around £600 when you include a hotel, food, drink and petrol, when you book a 'cheap' day.
The car is my daily so no silly mods which make it uncomfortable for daily use or excessive hassle for insurance and replacement parts. I have done 22k in the 14 months I have owned it and the only thing I have done is change the rear anti roll bar drop links as one of them popped out of the knuckle.
I'm looking at the 350z as I fancy a change of car similar to you plus i like the looks and sound of them, I know it a bigger heavier car but will it stop me using it on track, no. You just drive to the cars/your limit.
As for buying a clio, they are fun cars but a fwd on track isn't the most fun you can have and the feeling you get from a rwd through the corners on the power where its just moving around nicely is what makes driving fast fun, for me. A car that is planted all the time isnt as rewarding to drive.
I went from an E39 M5 (400hp 5.0 V8) to a CTR ep3 (200hp 2.0 4pot) so on paper its half the car, but I still own the ctr 2 years on as its such a laugh to drive, torque isnt everything, it just makes normal driving easier to cope with so you can be lazy and leave it in 1 gear, is changing gear really that much of an issue?