@Prettymetty i think you can do both in one challenge. Some can do no buy and others can do low buy. The trick would be maybe to create separate types of low buys? Holiday versus budget. I think I purchased one hair related product this month. So, budget wise, I'm good, but I only got the product because I could. Otherwise, I've been doing holidays. January and February I stuck to holidays as well.
I also would not allow the budget to carryover. But it needs to be a lower budget.
Even $100 over 12 months is excessive. I'm going on 6m on one bottle of shampoo and conditioner takes me through 3 wash days. I don't think WNG are even that expensive to maintain.