Hi Angury,
I recall starting with the Witches. My two favourite characters in Discworld are Granny Weatherwax and Sam Vimes. I found the first book, The Colour of Magic hard to keep my interest but enjoyed the rest of the series. When it comes to the Sam Vimes arc there's Guards Guards, Men at Arms, Feet of Clay, Jingo, Fifth Elephant, Night Watch, Thud and Snuff. If you skip one you may miss out on a bit of the Watch's story line. Some of the characters you'll meet are Nobby, Colon, Carrot, Angua, Detritus and Cheery.