For starters, there is no such thing as a "beginner spell" since all spells require massive amounts of concentration.
I suggest that before you even try to attempt doing any spells, you should first learn, study, and practice the basics to build a solid foundation... otherwise you may find your progress very limited. This site has multiple articles regarding the basics, and it even has a newbie central tab that you should definitely check out.
For your own study however, I suggest starting with finding a meditation technique that works for you, grounding, centering, practicing visualization, as this will become key later on when you actually do start performing spells, as well as shielding. Although shielding isn't necessarily considered a basic thing to know, but it is extremely important.