Sorry! No addons (unless some are made specifically for the new release of Warcraft Classic). Also, Bidding Is A Thing. There were bidding wars for the most expensive items on the AH, which you can only find in IF and Org. There might be bidding wars for the rarest of items on trade chat or the realm forums, for things such as the Hide of the Wild pattern. This drops from Dire Maul, Knot Thimblejack, by the way.
Only really to expand on Gráinne's comment as regards the 'collecting' and 'roster development' sections - which are, as said 'distinct' although they are intrinsically linked - I would like to point you in the direction of the in-game Achievements > Battle Pets > Collect tab. There are a series of achievements called Raiding With Leashes, pretty much all of which can be completed via the auction house - if you have the gold/inclination - or by completing old raids.