I started working soon after my undergraduate degree. Then, after a few years, I had the opportunity to do some TA work at Uni and it became apparent that I wouldn't have gone very far without a PhD. As I have an undergraduate degree from a foreign uni, doing a Masters was a must! So I did that and I am at the end of the first year of my PhD. It worked very well for me. I don't think I could have achieved so much if I had done it straight after the BA. I am much more focussed and motivated now.