The 'best' car depends on a number of extremely complicated considerations. Some cars, with the best driver possible, are better for a single corner, but not for all corners, for example.
Most drifters do not use 'drift mode', but just practice their drifting on their own. The drift mode is wildly inaccurate and not very useful for becoming a good drifter.
Improving your skill with a car is going to matter far more than having the 'best' car or tune, for beginners. Drifting is not like circuit racing where if you remove weight and add enough power and downforce even an idiot can put down a good lap time. It's about approaching limits that are already there, not trying to raise them.
As for cost, that doesn't matter at all.
For your level, the best drift car is something slow, comfortable, and predictable.
I have personally found the 1971 Nissan 240ZG to be the best drift car. Not because it will outdrift an LFA, but with me behind the wheel, I can drift any track, any direction, and never make a mistake and ruin the drift, for as many laps as I want, and in it, I can approach the very limits of what is possible in the car.