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.