Natural blonde going grey

I all I am 38 and my hair is naturally blonde but varies in shades from quite dark underneath and lighter on the top but generally quite an ash coloured blonde and I am cool to neutral toned and quite fair.My hair is really starting to go grey in quite big sections of hair underneath mainly,I am not really sure what to do as I will need to start dying it soon.When I was younger I went chocolate brown and it took months and months for it to grow out,when this was happening I could never find a blonde bottle hair dye that matched my natural hair colour.So I am now thinking what is the best way to cover the greys? Also I would ideally like to dye my hair at home as I cannot afford to spend hundreds of pounds a month in a salon,anyone have any suggestions?