The quality of captured wild pets is random. As of patch 5.1, upon entering a battle the Pet Battle UI shows the quality of a wild pet (idicated by a color-coded border around its icon). If you're farming a specific quality, if you forfeit the match your team will incur a small damage penalty (roughly 10%). There is no accurate way to determine a pet's quality prior to the start of a battle.
There are more passive methods to gain wow classic gold, but these are slower. For example, many people choose to fish in places like Tanaris, or kill Harpies in Feralas and loot items such as mageweaves. These are rather AFK-able, but again, not as rewarding. Some people choose to favour fun over anything, and like in any MMO (massively multiplayer online game), the best way to have fun is playing games with friends or your guild. Dungeon runs with your friends provide social interaction and are definitely helpful over the long-term for your gold stack!
Good question. Me personally, when I use a new strat from somebody else, I always read thru the strat, and in the case I really need to level some pet, I then (likely) exclude strats that are mentioning things like “RNG”, “risk”, etc. But: I’m always happy (when using a new strat) when I see some detailed infos, so that I can estimate what is going to happen. But YMMV.
World of Warcraft: Classic might be just around the corner, so it’s about time to start preparing. We’ve already published a class selection guide, and today we’re focusing on the most important resource of the game, of course, it is gold. Many players who played World of Warcraft back in the day might remember the times when you needed to count every spent penny and the times when gold farmers roamed the Azeroth on their super expensive epic mounts. In vanilla WoW, gold was everything. And we’re here to help you save as much of it as possible. So, without further due, let’s dive in our World of Warcraft: Classic gold making guide.
Although the Battle Pet Trainer will only offer to teach you your race-specific companion, it is possible to add all of these pets to your collection. You can either find them in your faction’s auction house or you can create a character of the race whose pet you would like to learn. Using your new character, you can seek out any battle pet trainer in major cities. After you learn the pet, you can delete the character; the pet you learned will not be removed from your collection.
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.