Reading from Jack Kearney's book here, human tracking would probably be best at first, if only because it's easier to lay out a track on easy ground, say a beach, sand quarry or dry dusty area for beginners follow, good area to get some nice clear tracks for drawing or measuring, general track description, step interval etc, a tracking stick could also be handy item here.
Perhaps a members suggested reading list of good track ID field guides or tracking books might be handy, feel free to add your reading suggestions.
Tracking Books.
Tracking: A Blueprint for learning How by Jack Kearney, a step by step guide with tracking exercises.
Track ID Field Guides.
Animal Tracks, Trails and Signs by Brown, Lawrence & Pope, a very good UK field guide. Out of print but only a couple of quid on Amazon.
Tracks and Signs of the Birds of Britain and Europe by Brown, Ferguson & Lawrence. If Ornithology is your thing this is the book. A bit big for a field guide but a great reference book.
Military Tracking Books.
Tactical Tracking Operations by David Scott-Donelan, X Rhodesian SAS Selous Scout.
Tracking, Signs of Man, Signs of Hope by David Diaz, SF tracking expert.
The Complete Guide to Tracking by Bob Carss, Ex-22 SAS Tracker.
Further Reading.
The Art of Tracking, The Origin of Science by Louis Liebenberg.