Please help! If you could get one purse

For me, definitely a Bottega Veneta Large/Maxi Veneta. Will this be your only bag? If so, get it in a neutral that works with your wardrobe, for me that would be the tan color family.
 
For 2k, there's quite a huge choice of bags that you can consider.
What kind of bag are you after? Something casual/formal/work ?

It's always good to consider the classics: Chanel, BV, LV, Gucci etc I think they would have enough choice of styles that would fit your required needs.