The basic story is Harry Potter learns that he has witchy powers and a mysterious past. Eventually, he will have to rise to the occasion and challenge evil and in the meantime, he needs to learn to grow and socialize as a regular kid with a dysfunctional family and extraordinary friends.
You will have to decide what format you are purchasing in as each has advantages. Read carefully as some have DVD extras and others do not.
You can binge or hold onto each rear as you grow to watch: YEAR 1: HARRY POTTER AND THE PHILOSOPHER'S STONE YEAR 2: HARRY POTTER AND THE CHAMBER OF SECRETS YEAR 3: HARRY POTTER AND THE PRISONER OF AZKABAN YEAR 4: HARRY POTTER AND THE GOBLET OF FIRE YEAR 5: HARRY POTTER AND THE ORDER OF PHOENIX YEAR 6: HARRY POTTER AND THE HALF-BLOOD PRINCE YEAR 7: HARRY POTTER AND THE DEATHLY HALLOWS - PART 1 YEAR 7: HARRY POTTER AND THE DEATHLY HALLOWS - PART 2
By the time you read this, you will notice that there is another series on fantastic creatures available.
I suggest you read the books first as they tell the fuller story. But do not let the privity of the movies keep you from having the fun watching Harry grow up before your eyes.
Some supplementary books by J.K. Rowling can and to the experience and books will point out that the depth of philosophe and Greek mythological creatures that J.K. Rowling drew from in here writing.