I used a turning plow, a disc harrow and a set of bedding discs for years before I got a 6' rotary tiller. The rotary tiller eliminates the need for the turning plow year to year and the disc harrow. If you can afford the tiller, I would advise it highly! Since you have sandy soil, plowing probably isn't needed any way.
If you add the cost of a turning plow and a disc harrow, you will have a good start toward a tiller. New or used throws all kinds of variables in.
When I was plowing, I would plow in the fall. Then in spring would disc the garden with a timber chained behind. The timber would drag and break up the clods and level the ground. A bedder would then be used to layout the rows.
Others will have different methods including the use of a 9 shank field cultivator instead of a plow and disc - this might work for you in sandy soil - use a drag behind it as well. Then follow with the bedder.
A box blade might work dependent upon how compacted your soil is.