Don't ever, ever get close to Racing Soft tires. Use sports tires for normal cars and maximum, Racing Hards for racing cars.
I've had this experience with some friends, they started using Racing Softs and had a bad path on letting them go. With sports tires, you'll have a good ammount of grip and yet good feeling of the car for starters.
Use the aids in low levels and turn them off in the way you start feeling comfortable without them. Most aids make the cars feel neutralized and that will remove the character of the car, making you don't feel important things as weight shifting, understeer, oversteer in their full amplitude. That's important for learning what kind of car you feel most comfortable with.
I usually recommend to starters to start already with only ABS=1 and TCS on lower levels (2-3) to learn how the cars behave then remove the TCS when you get better... But you can expand this hint with the other assists if you feel good with them, like I said, they really remove a good part of the fun and character of the cars...
The driving line is important and you can keep them on to learn the tracks... when you get the corners and speeds for the corners in your memory you can start removing them to start learning how to adapt your driving to each track and situation, even without the lines.
For starter cars, I would recommend FF cars for start, then 4WD and then RWD cars... the Mazda Roadster (Miata/MX-5) its an awesome driving school... get one in stock form and go drive it! If possible, with the less aids you can... it's a car that will teach you most basics of driving and specially, the basics of RWD cars...
Like some suggested, the Toyota GT86/Scion FR-S it's another excellent car to learn with...
And, before anything: HAVE FUN! I've said this already sometimes but, try to find the cars that best suits you... we can give you hints but you will feel what is best for you at your current skills... and this will evolve together with you.
Trust the small and low powered cars, they are valuable friends in your Gran Turismo journey!
But, first of all: HAVE FUN!
