Origin story: I had been playing 5e on the DDB fora. I was daydreaming about a street-punk-game world, looked at some non-D&D rules and landed on ICRPG. The simplicity and the advice here and elsewhere gave me the gumption to run something for the first time since AD&D and Traveler back in the 80s. I recruited 4 people from a game I was already in, gave them a primer, and sold it as a one shot. Here is how it went:
tl;dr we had fun but they are not converts to ICRPG
We played on the DDB forum because that is what I know. I am barely functional on Discord, and I do not know how to use the tools. But roll a d20, add something, and compare to something else, and if you succeed roll some other die and add something? That is what the DDB PbP forum does. And we were already there. Not having the right kind of character sheets, I put the necessary character info and some quick reference material on a shared google doc.
I had been thinking about a fantasy campaign already, so what I did was start in the middle, with a quest to correct one of the possible fail states I had come up with. That way the characters had a few milestones and neat stuff they could do from the start, since we were not going to get the satisfying jolt of progression in such a short time. And I could follow the “plan one session” advice, which is really the insight that gave me the courage to try.
I premade the characters but let them customize, and I had each player pick a treat for another player simulating a random past together. It was a basic retrieve a plot coupon plot: crush the skull of the late Matilda Wormface so her former coven members could renegotiate a better deal. Over 2 months / 292 posts they went through 3 fights, one skill challenge, and a social interaction with the big bad. They got some sweet loot from the second-biggest bad. One character frequently saved by the Chosen One ability, a couple other near deaths, not getting to go their preferred path due to bad rolls; it feels like they were appropriately challenged. They report that it was fun.
They said they would continue if I switched to “regular” rules, which stings a bit. Despite what they say, I think it is more about me as a DM and the tools than the rules. Roll a d20, if high enough roll more dice – it is not really different rules. Maybe the roll to cast system, but honestly that is so much better than use the slot, wait until tomorrow thing. But anyway, I did not argue, any parent knows well: you cannot convince someone they actually like what they say they do not.
Tools would help though. I know people play by post on Discord, but I do not know things like shared character sheets. I play in a game with the excellent Glocke, we use vtt and it is great, but that does not help with PbP. I have stuff to learn.
But big picture, I ran my first game since 85 and we had fun.