There are several different types of PEX and at least three types of crimp rings and tools. I have placed nearly 5'000 ft. of oxygen barrier PEX in a new shop building the past couple years and use standard fitting and copper crimp rings. Due to the scope of my project I purchased a crimp tool kit with 3/8", 1/2", 3/4", and 1" tool dies for around $125.00.
If you are doing just a few fittings, use the "shark-bit" fittings available at Home Depot. All you need is a cutter and preferably a camphor tool. The fittings do not leak and can be removed with a small inexpensive plastic tool.
Should you have more questions send me a PM. :)