If you want to get some cross-selling going, we can suggest gear such as the Welcome To My World Gym Bag and the Mammoth Mug, both of these make sense as a pre-workout/powdered drink cross-sell. Also, The 5% Funnel should be a standard suggestion for stacks that include any of the powders, it’s a very handy item to have. This means it could be one more cross sell with most of these stack ideas.
Back in my days as a retail supplement manager, we’d set up 5-6 stacks that began as a “Top Of The Line” stack and drop from there. I think the unique 5% line lends itself to buying packages, not just one item.