If I had the knowledge I have about them now, and was buying my first 20M car, it would be the Ford Mk IV. Very relaxing to drive with loads of character while being just as fast as the XJ13 and only slightly slower than the 330P4. The honorable mention in that category goes to the 250 GTO - just about useless as a racing car in this game without extensive tuning (which kills its character completely) but a very nice car to drive.
Similarly, when buying my first 15M car, it would be the Shelby Daytona. The same positive arguments as for the Mk IV but also noticably faster than anything else outside the "big three". Steer well clear of the D-Type, it's an oversteering nightmare. On the other hand the Miura, while not really worth its price tag, has the advantage of being able to be used in N class races... but I'd still pick the Shelby.
And as I've said in every thread about these vintage racers, and in this case it would be especially appropriate as you're not looking for a race winner, forget those racing tyres and use Comfort Softs. The true nature of the cars is much better experienced on them as the grip levels fall to where they were in the sixties.