My understanding is that there are three points of practice, self, other, and crazy wisdom. Theravada has come to represent the self knowledge, working out your own personal spiritual conundrums, which in tern, enable you to be more free and open to the world. Vajrayana is the crazy wisdom aspect, that there comes a time in life of non-thinking, spontaneous, out of your mind action. Mahayana is the bridge between the two, it is the compassion vehicle , doing things for other, embracing the unknown fearlessly and doing what is right for the collective.
For a good Buddhist practice, I am of the opinion that all three need to be addressed, Yourself, to enable you to help better, others, so your practice doesn't become a very nice shiny thing of no use, and crazy wisdom, which pushes you into the unexplored territories and keeps things fresh and renewed.
But, If I had to pick, Theravada is a good place to start, just sit and get to know yourself, your boundaries what makes you angry and why, get real familiar with this guy *points at self*, before considering if Buddhism is right for you. Use the Buddhism, to find out if the Buddhism is right for you.