Stock bike with a good raceable PT wheel. Deep profile clincher, for example, so you can train on it as well as race on it. A tall rear wheel is rideable in all conditions. If you can use your old front wheel, you can sell the new wheelset off your bike, easier to sell as a new pair than as a used pair or as a broken up pair.
Work on fit - seat, perhaps post, stem, bars.
Get good ancillaries - Pedals. Tires.
Replace wear parts with more durable things as they wear - chain, cassette, chainrings. You could probably keep the brakes for 10-20 years.
For riders with a quiver of race/training wheels, I don't recommend a PT. But for someone getting their first bike, I think a raceable/trainable PT wheel is good. Their stock software (a couple years ago anyway) works fine. You want to race and train on the wheel, else you won't know what you're doing in one or the other.
cdr