A spell is a prayer of a sort(some may disagree). There is not a level of difficulty per se, but one must understand how energy works and understand how to apply that information. A working of energy to help push for a desired outcome using your intent, visualization skills, and will power is what a spell is in lengthy form.
Though you did inquire of a simple spell, well it so happens I have an example for you.
If you have the following ingredients: lavender, sage, sweetgrass, or just one of the three herbs this will work wonders, however if you do not then there is no worry the spell still can be completed.
Use a safe container to burn one or all of the three herbs listed above and envision "negative" energy being pushed out of windows or doors from your home. You can see negative energy however you may like, I personally see it as a toxic sludge that is blocking the flow of energy throughout the home; a pollutant.
I use a white light to 'blast' out the negative energy by visualizing it explode like the big bang was theorized to do so. While the aroma of the herbs brings upon relaxing energies to bring a postive feel to the place.
This is a simple cleansing.