Unfortunately, you are not able to steal small amounts, its either nothing or the whole lot. Some advice for you my friend
At a low pickpocketing level, you'll be really bad at stealing any of it;
First you'll need to get your level up higher, and then you will see the % of items going up, also, you will want to acquire some perks in the pickpocketing tree.
My advice is to keep track of those with big money in their inventory, and only take smaller items from them, like food, keys and other invaluable items, thus putting your level up some what, remember to go to the guardian stones and select the thief stone to help your pickpocketing level rise that 20% faster, if not done already
Maybe invest in some items that put your pickpocketing up some percentages, like gloves, ring, Armour etc.
Or if you don't want to wear it all the time, buy a house and put them into your chest for when you do wish to use them, for when your brave enough to try again.
Always save your game before you try it, because you never know when they will catch you, sometimes the first item, sometimes the 3rd or not at all.
So hope this helps, good luck and go forth and cause havoc
Thanks for reading