I found a hairdresser who I trust, after all, she has the know how so that must be first on your list. Find a good stylist.
Next, go through the colour chart with her/him to see what (s)he suggests as a base colour and ask for flashes woven through.
I suggest delicate strands of a lighter colour, maybe toffee or a slighly copper shade (no, not red or ginger)
around the front and sides. Just a hint, which will warm your face.
As you get older, pale colours wash you out and dark colours make you look hard as do block colours.
Blonde flashes go like straw, believe me, I've done the lot and it looked like one of those thatched beach umbrellas when I washed and dried it myself...really
My own hair is medium brown going grey at sides and front but still brown at the back and I used to dye it myself 'Deep Reddish Brown' as my normal brown hair tends to have reddish tones. It went darker and darker.
Now I have it a warm conker brown with copper flashes blended in on top sides and front which look entirely natural. I have the back layered from the crown and into the nape to give fullness and the rest is over to one side and pushed behind my ears, just ear lobe level.
I would never have chosen the colour on my own and yes, it is an expense but it's my treat every 5 weeks. Cut, roots or flashes, wash and hair masque and dry. It cost about £54 with the 20% off January special.
I haven't been so pleased in years.
Do take the plunge and good luck.
Let us know how you get on.
I'll post a photo when I have mine done again in 2 weeks. 