As a general rule of thumb for buying packs of a set, the first 60-80 packs has the biggest payoff for expanding your collection, after that, the value starts to go down as you get more and more duplicates.
I’d second this. (Though TGT? really?)
You are not likely to get the 1 of 3 Old Gods in Whispers of the Old Gods, or the top 3 of Kazakus, Aya, and Patches from MSG in a pack for example, but will get some other legendary.
I’d recommend crafting the few legendaries you are looking for if you don’t get them, probably neutral/tri-class ones before class ones but it also depends on what type of Wild deck you want.
For Wild, Zilliax is less essential than in Standard but still very good. He is just a decent card to have at the 5 mana slot that functions as removal, healing, and stays on the board afterwards.
Probably top priority if you are still missing him out of those 5. I crafted this one Week 1 of Boomsday.
Siamat also functions pretty nicely as board control, or a threat the turn you play him, but being at 7 mana you can adapt your deck without him. I still don’t have this card.
Zola the Gorgon is very useful. Youthful Brewmaster is like a budget replacement but you lose more tempo doing so. I crafted this one as part of Quest Rogue but I ended up using her a lot more in other decks.
Zephrys is quite good, but I think the hype around him is starting to die down. If you just have this one card though, you make a deck with no/few duplicates worth the payoff in the long game. A very cool card.
Kazakus is just so useful, you can play him on Turn 4 and get a 5 mana potion that can deal a lot to your opponent’s board, and that’s just one scenario. I did try the Reno Mage archetype before I crafted him and I did still win, but if you want to play any Reno Mage, Priest, Warlock, he’s high priority.
As an extra read, I go into all the sets here: What to buy in wild packs - #6 by Jonius-11264