This is a tough one as depending how old the car is it may need a lot of work... realistically you need multiple stages to detail and perfect shine.
However if you really want a one step process at least buy two, turtlewax colour magic the same as your car colour as it is actually very good at hiding poor paint. Followed by a good wax such as colonite 476 (hard wearing but not too hard to apply)
This is probably as little as you can get away with and still have good finish.
The key to a good finish is the preparation so two bucket wash with a lambswool wash-mitt
(please take a moment here to burn your sponges!)Clay your car to remove contaminants will help smooth your paint and thus the wax will stick better and longer to the car.
Polish will remove swirl marks, marring, holograms etc all paint defects but this is the long process, turtle wax will most certainly help remove but mostly cover and fill these.
Colonite is a great synthetic wax so will give a deep reflection, carnuba and natural wax will give a deeper shine but less defined and deep reflection... FYI
my general rule is darker the colour go synthetic
Synthetic 
Carnuba
Hope this helps,
Good luck and stick some photos up after!
