Originally posted by beachgardener K3 with a Tamron 17-50 f2.8 is a good start, gives you time to work out which lenses you need, old, used or new.
To the OP: You will get 100 different variations on what to buy based on other people's experiences and preferences as to how they shoot.
That said I am with beachgardener. The tamron 17-50 would be a fantastic place to start. I assume you don't have a lot of photography experience otherwise you would not have posted a 'which lens' thread
For me I started out wanting all zooms and I thought the bigger and longer the better. Fast forward after owning a few of those and I shoot all primes. Lens selection is a matter of 'the job' you want done and sheer personal preference. Preferences must be honed and learned through nothing but trial and error. No one can tell you the right answer for you, only that 'X lens is of good quality/sharp/cheap/best value' etc etc.
The 17-50 gives you a wide range in one package and it's a sharp lens. Later on once you've shot for 5 or 6 months you can see what you like and don't, or if you want to try primes (and of which focal length) and so on and so forth.
This is by far in my opinion the most economical way to start out. Otherwise if money's no object just buy a bunch of lenses and test them out, but I suspect that it would wiser to not do that.