There are some lines, such as complications ( one per brand ), or themas ( Chronos, Chronometers, GMTs, Minute Repeaters, Alarms, and so on ), or one brand ( all the watchesz of a brand ).
There is another line: Buy what you like.
In any case, take your time, read some articles on watches you like, TRY them,... Take your time as learning to know the watch you desire is a big part of the fun.
Enjoy!
Nicolas.