I think VGT is precisely the map that will show you the limits of The Earthmother's boons. At least I stopped relying on her just when I wanted to win VGT for the first time, and switched over to GG as a "general-purpose booster deity". GG gives you +5 base damage and +8 health plus whatever you can grab via Absolutions (and you don't really have much use for L1s beside clearing curses, coincidentally GG can also do that; on top of clearing away Weakenings and Corrosions).
Or Taurog -> Dracul.
Going in Purist one big dilemma I have is that there is only one curing potion I can buy (or I have to wait until a GG cleanse becomes viable if at all). Even only 5-6 stacks of Weakening and/or Corrosion are problematic. If you don't go in Purist, Apothecary and/or the right curing potions probably make a lot of sense.
Patches is a bit double-edged. I think it works reliably on Crusaders and Vampires, but I'm not sure I'd hazard it on any other build, simply because it adds another element of randomness into an already very random and arguably even quite dangerous map.
EDIT: if you just want to win VGT, take the Vampire build Astral & I used for the VT, I think it's a very solid build and given how it can take VGT even despite the VT, it should be fairly straightforward to clear non-VT VGT with it. You need to make sure you keep 3-5 blood cows (i.e. monsters who you cannot 1-shot KO and who are not bloodless) and use their health regeneration to replenish your health. There are some more difficult levels and opponents, worst is clearly the Bloodless level, but the No XP or the pre-explored can also pose difficulties. That said, unless you're outright screwed by RNG, you should have enough staying power to conquer VGT...
EDIT2: btw what's normal number of attempts to clear Purist? I've already tried twice and I only got as far as Towers 3 & 4 (had terrible draw both times, though). I think the most number of tries I took with anything before was around 4-5, but this Purist just seems a magnitude more difficult...

EDIT3: *!#&%! My third attempt ran out of steam at Tower 9. Dancing Blade is just plain murderous at +90% stats.

"Thinker", just without the "ache".