Welcome to Tableau!
Tableau has a pretty good video on waterfall charts already: Waterfall Charts In fact, if you have time- spend some looking through their training videos.
Also search "Andy Kriebel" on Youtube. He will get you started with some more fun/complicated visuals.
As for showing YoY sales, would a basic YoY bar chart suffice? Something like this? Tableau Tip Tuesday: How to Display KPIs Next to Bars
I hope this helps!