In my opinion a mantra on its own is not much good. A magic spell has 'power' whether you understand it or not. I don't think mantras are like this. Just finding a mantra on the internet and chanting it is of doubtful benefit. If you absolutely must do it, then go for something simple with lot's written about it by a range of well known and well qualified people. You are not so special, or in such a unique situation, that the oṃ maṇipadme hūṃ mantra won't suit you fine.
If you don't feel you understand a mantra then don't use it. If there is no one you can ask about it, face to face, then it's probably not the practice for you. Translating a mantra often just trivialises it, and misses the point. Find a teacher. If there are no Buddhists in your area then try http://www.wildmind.org/.
My website is a resource for practitioners and I don't recommend using it as a sweet shop for collecting mantras, or for choosing mantras at random. I think all Buddhist practices require regular contact with more experienced practitioners.
Don't cheat yourself.
Mantras are not magic spells.
Find a teacher.
This is my advice.


However in the Hevajra Tantra (ca. late 8th century) this first word takes on esoteric significance. I think this is largely related to the shape of the Siddhaṃ script letter 'e' which is an inverted triangle which in the Hevajra becomes a yoni symbol - i.e. because it looks like the female pudenda it represents the feminine principle. To my eye vaṃ is not particularly phallic, but it comes to represent the masculine principle. Perhaps the most significant correspondence is that of wisdom and compassion. So evaṃ, by combining the two principles, symbolises the union of opposites which is one of the ways in which the Buddhist goal is conceived of in Tantric Buddhism. This is my understanding, though Tashi has more information on his website.