Unless you fully understand how the CMYK system works or have instructions on how to use the system you will be open to some disappointments not to mention there is a good chance you will waste alot of paint trying to match colours.
I would recommend you simply get the three primary colours red, yellow and blue along with white and black, also invest in a colour wheel, it will show you at a glance what colours you get by mixing any two or all three of your primaries, it will also show you what happens when you add white or black to the colours you have mixed, you don't need orange or green since you will get these and purple from your three primaries.
If you are still hell bent on the CMYK colours, study the system first before throwing your money away, but as Andre pointed out you don't need black with this system since these colours mixed together make black.