Before working with magic or spell casting there are some key things you need to know:
*Belief in yourself and your abilities
*Circle Casting and Releasing
*Correspondences (colors, days, lunar phases, etc)
Please keep in mind that depending on who you talk to the basics can and often do differ. The above list are the basics that I studied when I first started practicing and are what I teach my students. You can add to this list or take subjects from it depending on your interests or what you feel you need or don't need to learn. However, I suggest studying all of them because you may very well need to know them in the future.
As far as which spell is easiest, that depends on the individual. Some find certain spells easier than others. I would try a few protection or luck spells for starters and then go on from there. Just be careful when choosing spells on this site, as the majority of them wont work. It's far better to write and cast your own spells.