From the sheer amount of Questions and replies I would say that there's more confusion and controversy concerning this achievement than any other. Now, before I go any further let me just say that no, I do not have any definitive answers but I do have White Wolf up to level 4 now and DO have some thoughts about it and maybe some advice. 

First. From MY experience the level of Invaders you have to hit is moot as 99.5% of the Invaders/Ghosts I've hit have been level 1's. That percentage may even be a little higher tbh.

Second. Contrary to some accounts I've seen both in here and on Reddit and facebook you  DO need to hit Ghosts in addition to Invaders and Ubers. Level 1,2 and 3 of White Wolf "seem" to need only one of each. You'll see why I bracketed "seem" in a second. For level 4 (my newest level) its 3 of each. At least that's the minimum I personally have hit on a few of them. After that I'm as in the dark as most of us it seems. 

Third. And here's where I may get some blowback lol. In MY opinion I wouldn't worry too much about setting this particular achievement as a PRIMARY goal. At least for newer players and the lower levels of it at least. I'll give my reasoning on this now.....

Fourth. IF , as you should, you set the "Hunt Has Just Begun" achievement as a primary goal the White Wolf will come as a by-product, as an "extra bonus" if you will. The sheer numbers of Invaders/Ghosts you have to kill for The Hunt pretty much makes getting White Wolf inevitable with the added bonus of the VAST amounts of Gold you can get. Yes, it takes awhile to get The Hunt achievement and yes you WILL need to use close to half that gold to get the next level. I did not (in a glaring oversight!) write down the numbers for either of the amounts of Invaders/Ghosts needed per level OR the amount of gold you get until level 5. I won't post those numbers here but if you're interested just message me. Suffice it to say that the last 5 levels will net you 314.5 million gold. The last level's gold is "all yours" too as you won't have to save any of it back to advance to the next level. For newer players and hell, even more advanced players that is a NICE amount of gold to play with. Use it for knowledge upgrades, building upgrades ....anything you like. 

To sum up. The Hunt Has Just Begun requires many thousands of Invaders/Ghosts to get. You will NOT get it in a week or even a month or two (maxed). The VAST quantities of gold available WILL help you in all other areas of the game. That's not even taking into account the materials you'll get which you WILL need anyway for gear for your Hero and Shaman(s). As a by-product of getting this achievement you are pretty much guaranteed to get some White Wolf levels. 

So , get out there and start hitting all the level 1 Invaders/Ghosts you can squeeze out. With the gold you get from the first few levels of Hunt , buy Hero energy and hit some Ubers. "Tip" - pay attention to how much energy it will take you to kill each lvl 1, multiply that by however many lvl 1's you'll need to reach each new level of Hunt, save that much gold back and use the rest for, relocations as you'll need plenty of those and anything else you may want/need. Once you start the ball rolling White Wolf WILL happen and maybe by the time more people start getting it we will have more accurate information on what the mid to higher levels will require. "The Hunt Has Just Begun" is by far the best achievement to strive for , imo, for new players and hell, for mid-level and higher players too. Good Luck and enjoy the game