Most platers will have a minimum plating charge so get it all of your parts done in one go if possible not a handful here and and a handful there. Also when we get plating done at work, if we want a bright finish we don't shotblast the component but if we want a dull finish we do shotblast it.
Finally if you do go down the stainless route by your fasteners from a proper dedicated fasteners supplier as you will get the best prices and if you pay cash they shouldn't bother with minimum orders. Most of the smaller sizes (M4, M5, M6) they will prefer to sell in bags/boxes of 100 but biggers sizes (M8, M10, M12) they will sell in smaller quantities such as tens.
If you are in the Northants/Bedfordshire area i can recommend Anglian Fasteners Ltd, i have used them for about 15 years and find them to be a good company to deal with.