I'd suggest watching the classic Black and White era first, however, there are lots of Lost Episodes from that era that you cannot watch at all, because the footage of those specific episodes have not been recovered. There's an entire part of the show, where one of the Doctors only has one or two episodes that still exist, for you to watch, which have destroyed that character's development.
For further information, the "Doctor" character switches into an entirely new character, besides the charisma and outfit designs, (which are basically the same, besides maybe a few pattern changes, and some color changes.) every few seasons. So, for example, a single version of the Doctor might only last one or two seasons, sometimes even three.
And, if I was to be very specific with how you should watch the entire show, I'd suggest watching all of it, besides some of the weird ones that might gross you out, such as the one with a villain named the "obsorbaloth". (If I'm not spelling his name right, please correct me on that.) Overall I'd suggest doing all of that, if you'd really like the best experience with the show, the show has also experienced times where the quality of the show went down for multiple seasons, all because of a single change to the Doctor.