If you're looking into getting inot clasic who, I'd highly recomend these serials:
Tomb of the cybermen- because it's a clasic and is generaly brilliant. If you like 60s and 50s sci-fi, you'll absolutely love this one. If the Moonbase didn't have any lost episodes, I'd probably recomend that too along with the tenth planet.
Genisis of the Daleks- because it's a clasic, personaly it's not one of my favourates, but it is one of the most famous serials ever. I do recomend everyone to watch this, it's just a personal thing about 70s who I don't like though, that's all.
The Three doctors- because it's a clasic, is really enjoyable, and is just so much fun to see, I love 2 and 3s relationship. My favourate Petwee story without fail.
The Green Death- becaus it is just so good. Fine, "it's the one with the giant maggots", but still, the story is so good, and it does work its way up to being a clasic. Is also the first Pertwee story I ever saw.
The Five Doctors- because it's a clasic and is annother fun episode. The Master is fantastic in it, and as well as bringing back the old doctors, it also brings back some old companions.
The Two doctors- not because it's a clasic, but because i found it fun. Colin Baker at his best, fine alot of people can't bare any of Colins stuff, but I for one feel fond of some of his serials, and this is definately his best.
The Dalek Invasion of Earth- because it's one of the daleks most famous serials and is pretey cool to watch.
Earthshock- not because it's a clasic, but because it's a fun serial, and shows Davidson at his very best, and an awesome cyberman epic. It was also the first clasic serial I ever saw, so it has personal value to me. Watch it dude, you will not be disapointed.
Remerberance of the Daleks- because it's the last dalek story in the clasic series, and is fun to watch, also a bit of a clasic!
The 1996 movie- Fun epic with the master and a personal favourate. Then again, it is closer to RTDs stuff then anything else, so you may not like it, I however love it. It's worth a chance though.