I have always used dignities in the past, but am considering using reversals, at least for a time, to see how I get on with them. As I've never used them before, I won't know whether they're effective or not until I try it. It's up to you really, but I like the idea of using either dignities or reversals, as it gives another dimension to a reading. Saying that, it's probably best to become familiar with the upright meanings first if you're a beginner (you don't say if you are or not).
Edited to add:
Just noticed your question asking about dignities. It's basically a system which can be used instead of reversals. It works like this:
If neighbouring cards are of opposite suits, they can be considered ill-dignified and the 'reverse' meanings are applied. Each suit relates to an element, it is the opposite elements which makes them opposite suits. Therefore Cups and wands (water and fire) are mutually hostile, likewise sword and pentacles (air and earth). Other suits are neutral with each other, but suits of the same 'sex' are more supportive than those of the other sex. eg. Cups and pentacles are female, wands and swords are male. In addition, the meaning of a card can be sweetened or soured according to it's proximity to 'evil' cards, or cards who's meanings put a negative slant on things. It's a flexible system up to a point, but it rules out the possibility of certain cards being read together in other ways as they are controlled by dignity. I tend to play it by ear and make sense of it intuitively.
Hope this helps.
Zoe