Heyo!
First off I commend you for taking the initiative to want to apply for Helper, and it's always cool to see that people want to help out the community! I would suggest however that you don't rush to meet the requirements, but instead take your time to really learn as much as you can about the Parkour server as a whole. This way, you'll be more prepared and you'll probably also find yourself more ready than you would rushing to get God as soon as possible to meet an application requirement. I actually just ranked up to Insane yesterday and I still feel I have a lot of ways I could get better at parkour, so I would try to focus on your personal knowledge and skill rather than just looking at a rank.
As for Champion maps, I believe I've seen a post similar to this one in the past, and I remember that it was general agreed that out of the current Champion maps available, Aquatic is currently the hardest, however there was a bit of debate of how to rank the other two. In my opinion, both Haunted Manor and Winter Wonderland are about the same difficulty, and I really enjoy the difficulty level they both offer since they're not incredibly difficult, and it allows all players to have fun with some of the bigger maps on the parkour server. In summary, I would say either Winter Wonderland or Haunted Manor are interchangeable the easiest Champion map. I believe there's also more Champion maps soon to be added, so hopefully you'll be able to have some fun with those as well!
Thanks for reading and best of luck,
- Icebarge