No worries, you've come to the right place to ask :D
1. The custom raffle by Paz is free to enter, and so is the premade design by shibakiba. Just be sure to read through the requirements (joining the world, fav-ing).
We'll also host flat sale (paid) staff customs in the future, though details on that would be announced in a bulletin + you can choose which artist you'd like to commission, while the artist also picks which concept they would like to do. Prices would vary but range somewhere around $60++

2.  Yeah! We'll have an unlimited common MYO charity sale in June, with decayed slot upgrades raffled off at random when we hit milestones. You can also upgrade your ticket fully or get one decayed trait through shop items. Decayed MYOs currently are not being sold, but through event participation and prizes.
On upgrading - you'd have to upgrade the ticket before submission or apply the decayed trait with an item. A fully common naut cannot turn into a fully decayed naut after the design has been approved as generally we want trait to remain within the same tier after approval.

I do recommend joining the discord as we sometimes host flash giveaways, events/sneak peeks and the booster chat has monthly raffles, though all major news is posted on Toyhouse. We just have goodies if you do decide to join. If you have any further questions, feel free to comment here again and thank you for your interest <3