I think you would be really happy with a Black City with the regular hardware. It goes with everything, is a great size and is not likely to go out of style. Be careful though... these Bbags and tPF forum are really addictive!
A black City is always a great first bbag. It's very classic and pretty much goes with everything. I convinced a friend to get this for her first bbag and she just loves it to death. If you like big bags, the Work is really great too, I have one that I use for work, but it's too big for the weekends for me. I do have to say though that I recently got a Part-time, and it's the perfect in-between size for me because I can use it for both work and the weekends. You might consider that, but if you want a true classic, I'd go for the City.
No bbags are "old lady bags" due to their design, imho. The city is a great size to carry as a day bag and with the rh is not too trendy/blingy, but just trendy/blingy enough (if that makes sense). If you like smaller bags then you might want to look into the twiggy and if you want something a bit bigger then the part time is longer than the city, but shorter in height.
City in black sounds good as a first choice......although the Day style is rommier but can only be carried on your shoulder (well, you can wear it by its handle too but it´s longer). If buying a balenciaga you will never end up with an old ladies style anyway they are all cool! Good luck with your pick (it´s hard because there are so many gorgeous bags!)