As someone who spent months in VMOL to earn the Maw skin, I can assure you that you will need to either learn the mechanics and start with a dedicated trial guild or pay the 3-6 mill gold to just be added on the last boss for completion. Most trial guilds won't just accept one new person to get them the skin and then say goodbye out of the kindness of their heart. You have to earn your place in a guild and show the dedication and skill before doing hard content.

I personally like the Amberplasm skin in Mazzatun as opposed to the Spiderkilth Skin in Cradle of Shadows but with the next patch, both of these dungeons are being nurfed so should be a little bit easier. You will just need 3 others who are as interested in the skins as you are!

In the future, I believe they will have a new skin in the crown store again for Halloween or with the next crown crates which looks to be Halloween theme. That's how I got the Mind Shriven Skin last Fall.