This question is asked of me very often. There is no one correct answer. The answer depends on what you want to do with handplanes. The most common use for benchplanes in the woodshop is taking a board from rough to finish. This takes three different cuts, and therefore three different planes.
The first cut is the rough cut. This takes a board to pretty near finish size and roughly flat. For this operation a fore plane, usually 14″ to 18″ long, is used. A good choice of fore plane is a jack plane. The Stanley #5 being the most common and easiest to find is 15″ long perfect for this task.
The second cut is flattening and this is accomplished with a jointer. The Stanley #7 is the most common and easiest to find and at 22″ long is well suited to the flattening of boards. A #7 1/2, or #8 would also work well for this cut.
The final cut is the finish cut and this is the finest shaving you will usually make at 0.001″ to 0.002″ thick. This cut is best done with a well tuned Stanley #3, #4, or #4 1/2. For a beginner I recommend the #4. It is the most common and is easy to find and inexpensive.
There is one other plane that I highly recommend in the woodshop. No shop should be without a block plane. If you are only going to have one block plane make it a low angle plane such as the Stanley #60 1/2. This plane will handle all of your small plane needs as well as planning end grain with ease.
If you are a real beginner I published a review of Chris Schwarz’s DVD “Super Tune a Handplane” in June of this year. That is a great resource for anyone wanting to buy antique/vintage planes for use in the woodshop. Also, I am working on an article on sharpening for the beginner.
I think the best plane for a beginner to start with would be a #5 jack plane. It is easier to tune a plane for rough cuts than for fine finish shavings. And with some experience the #5 can be used for many other cuts, even finishing.
As always thank for stopping by and please feel free to leave a comment.