Ooh, you've seen a fair amount of Classic Who, then! I really do suggest Tomb of the Cybermen, since you haven't seen Two in action yet. I'm really glad you've already seen some of Four and Three's best. ^_^

Well, I always like to see a doctor's first serial, so I'll definitely start with Rose, and Muppet has mentioned Empty Child a few times, so I'll go to that two-parter next. Is there anything I should know about the episodes in between?