I registered to say thank you for this guide. I've progressed in the way you suggest: Firecell, then semi-unupped Limitless and then upping everything, one by one. I'm now happy to say I have a fully upped FG grinder (of course Limitless is not the most efficient out there, but I still don't have all those shards), and it has been a fast process so far. Btw, Gemini and Scorpio are not that hard even without Purify or Lobotomizer, they just need a good hand and some Sanctuaries in play.
I'm using the fat unupped version, but upped
Probably gonna buy some more upped Hourglasses, Time Pendulums, Purify and upgrade my two Lobotomizers to make the fat upped version described in the original Limitless thread, and then start banking some gold to build a good Arena deck. I tried a little bit of Arena play using an unupped Psiontal, it gets spins every hour but I suppose it would be much better if I got better cards before hunting for rares.
Well, I can't wait to have a good pool of cards to start applying my own ideas for decks, but I'm gonna stick to this guide by now to get some more upped cards and rares.
Thanks for all the help your guide has been giving me!