I've tested all of the unupped FG grinders except Rol/Hope and they all hate me and I would recommend none of them.
I have heard good things about RoL hope, but it's certainly not used as much as LS or firecell or one of Chapuz's other decks, which is probably an indicator of a minority for whatever reason.
Use what works for you. If your unupped monoentropy can somehow grind plat, then you might as well use that.
What I would do is stick to bronze/AI4 with the unupped grinder of your choice, look at your shards, and depending on what shards you have, save up and build one of either:
-Pdials (6 SoSac and 3 SoD)
-Swallow (4 SoFo and 3 SoPa)
-Brave Freedom (6 SouFflé and 4 SoBra)
-Speed Poison Kamikaze (5 SoSac and 6 SoBra)
And then go to town on Gold/Plat.
Those things have been proven to work, typically.
Just remember to try different flavours until you find something you like.
You can make more mistakes and buy more failures when you have an upped grinder, so it's a very good idea to get one first before experimenting with other fancy decks involving upgrades.
After that, otyguh decks... Well, Swallow.
Otyguhs are much better upgraded - you'll barely need to buff it up.
I question what entropy/gravity would do for you, though:
Chassis
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Try something like this when you want to make that deck. I'm sure other people will help you. Just make an upped grinder first.