I tend to plan carefully then end up planting what I fancy on a whim.
As you're a newcomer just plant what you think you'll eat, keep a few notes then next year you can tailor it better to what you will use.
'Quantity-wise', its difficult to get it right. You'll plant what you think will be enough, have a bad year and won't have enough. Next year you'll plant more, have a bumper year and yield too much. Anything you really like you will never have enough of, I'm sure my wife would be happy if I put the whole allotment down to strawberries.
Any surplus this year will be gratefully received by friends and family. Or get some chickens, they'll certainly accept your surplus. There's usualy a way to store some of your surplus as well, almost as much fun as growing it.