I "borrowed" *ahem, stole* this lovely little cross body bag from my mother. I was actually lucky enough to be gifted my own Mulberry bag last year (the Roxanne) but it tends to be too heavy for everyday use. I don't really carry much with me on a daily basis so I find something compact and light to be an essential.
I believe bags are one of the best investments you can make (fashion-wise); an expensive usually both timeless and long lasting so you are guaranteed to get your money's worth, as opposed to a pair of shoes which could go out of fashion in no time. I think it's always best to chose a neutral colour, think tan, brown or black, as this maximises the versatility of a bag.
Of course, you don't have to spend a lot on a well-made bag; they are also readily available on the highstreet. Topshop has some lovely leather bags at the moment and if you are willing to search for a bargain, try TK Maxx.
Would you invest in a designer bag? What's your everyday bag?