I never bought the first season myself, because while there are some good episodes, there aren't enough to justify the expense, plus the characterisation is terribly uneven. Otoh, the second season sits snugly on my shelf, and I definitely would recommend it. (And yes, you can start with 2.01.) There is just one boring episode in it (err, the Ianto-centric one in later s2), the characterisation is solid throughout, and while there are individual scenes or some such I didn't like, I thought it was a good season, and it contains some of my favourite episodes. It still didn't prepare me for the quality level in Children of Earth, but it's good.