QFC was originally designed with the deliberate intent to make a challenge friendly for newcomers to the forum. Quick rounds make it easy to get feedback, simple challenges make it easier to meet the rules. The only issue is that you need to do it quickly.
Alternatively, ALC and LHC are both challenges with a lot of stuff, but you can just focus on the most recent post’s rules. I host ALC and am happy to answer questions for newcomers, and I am pretty sure that cake_ape (who hosts LHC) is happy to answer questions too. The bonus of those two is that you can enter just about any car in those two challenges.
Finally, I highly recommend joining the discord and asking to collaborate with other community members - it’s a great way to learn and lets you look at their methods!