In terms of locks to practice with what you're looking for is a low security cylinder for a deadbolt or nightlatch which will typically have only 5 pin stacks with no additional security features.
Have a look at
Illusion's repinning guide for an idea of what it is you're going to be looking for in the store then go and get one.
If you can, pick up a "replacement cylinder" which is the only thing you're wanting otherwise you'll have to buy it as part of a complete deadbolt package. Kwiksets are fairly common in the US and easy to pick so good to start on. Get one of the low security models like the 660. The ones you buy will have a tailpiece fitted to the cylinder which should come out when you remove the circlip from the back of the lock.
