Merchandise Line Design

I am seeking expert advice on developing a merchandise line for our nonprofit, including items such as tote bags, stress balls, magnets/stickers, and t-shirts. The goal is to create products that align with our brand and resonate with our target audience. Specifically, I need guidance on:

Designing cohesive and eye-catching products
Selecting the right materials and suppliers
Choosing the most effective items to distribute at events to maximize engagement and brand visibility
Budgeting for these items
Developing strategies for effective distribution to create a lasting impression

Your insights and suggestions would be greatly appreciated.