This grind is not for the unskilled lol.
GS grind = u can win and make progress or lose and go back a few steps.
I.e win 3 TT matches against king elmer but lose 10 times.

Relic grind etc. = you grind and grind grind slowly making progress but there is nothing that will give u "negative" progress.

So u can have all the time in the world trying to grind GS mgp but it won't do much if u suck at the games. Best advice is to take time and get good at triple triad, GATES or try the choco racing route and invest in it hoping the payout in the future will be worth it.