I've found that spells are almost always most effective when written by the caster, so I would certainly suggest that. The following is the link to an oft recommended forum post written by Lark on how to write your own spells.
Black candles can be used for protection rituals.
Oak and aloe vera are associated with protection. Lavender is often used to bring peace to a household or person. Clover is associated with luck, which might be helpful. As stated above, sage is often burned to purify a space (it spells a bit like marijuana, though, so be forewarned). You can make bundles of herbs and plants and hang them over your door, put them in a pouch, or you burn them as an incense (be careful with the last--some plants are too poisonous to be burnt, so look up the risks first). Mistletoe is also commonly hung above doors for protection.
Amber and tiger's eye are both quite common in protection spells. Quartz is often used as a conductor, and can make spells more effective.
I have a friend who only does protection spells on Tuesday, as it is associated with protection.
If you feel the Moon phases affect magick, perhaps line it up with the waning or full Moon.