A stock, like proper grammar, is important for a lot of reasons.
It's hard to aim a pistol grip shotgun with no stock. They do need to be aimed.
It is easier to properly cycle a shotgun when you have a stock against your shoulder and there is less chance of short stroking it causing a jam.
Faster, well placed follow up shots because the gun will not move around as much when cycling it.
Get a youth stock. Easier to handle indoors and still easy to operate. Pistol grips cost more because they are tacticool.
^What he said. A lot of good recommendations there.