Black 35cm Gold HW in Togo.
Goes with everything, can look smart, stylish, chic, posh, yet edgy. Low maintenance.
Lighter colours like Etoupe or Gold can get dirt on visibly or Jeans may bleed on them? But Black can go everywhere and will be fab for a first Birkin.
If you are petite, consider a 30cm because that size is prettier with dresses on smaller-framed ladies.