The first one I got to watch properly was Wrestlemania 2000 - not the best to start with tbh. Basically all tag team matches bar the main event and a "Cat Fight"
Wrestlemania 17 and 18 always stay special to me though, they were awesome.
Especially Hogan vs. Rock at 18. Probably the best I've ever seen a crowd "invested" in a match, just constant cheering and screaming for about 30 mins.