Stick to firm fruits and vegetables
The first rule of Spiralizer Club is: You do not talk about Spiralizer Club (seriously, people will make fun of you). The second rule of Spiralizer Club is: Avoid spiralizing soft, squishy foods.
My machine came with three blades: number one for cylindrical spaghetti-shaped noodles, number two for flat fettuccine, and three for thin, ribbon-like strips. I found that the best, most versatile foods were fruits and vegetables with a firm composition -- carrots, potatoes, apples, beets, squash, and, of course, zucchini. Those crunchers held up perfectly no matter which blade a chose, and cooked quickly and efficiently without turning to mush. These guys also stood up to sauces and spices while still maintaining some of their own flavor.
Some semi-soft produce can work, too
Medium-textured or somewhat watery foods like cukes, bell peppers, pickles, pears, cantaloupe, and strawberries can also work, but these required some more work on the front end -- chopping up into chunks, peeling, coring, seeding -- that kind of thing. I could also only really use one or two blades when working with these slippery suckers and if I tried pushing them through too hard, they mush-ified or straight-up refused to go through the grate. The number three (the ribbon) and number two (fettuccine) blades ended up being the most effective. However, once I figured out which blades to use with each fruit or veg and the proper amount of force to apply, these made for some of the best spiral dinners I ate.