Begin with leaves
Indoor hydroponic guides often recommend leafy greens and herbs because they can fit smaller spaces. Pick a crop you actually enjoy eating. One variety at a time makes it easier to notice what is working instead of managing several unfamiliar plants at once.
Further reading: Illinois Extension · Getting started with hydroponics at home
Plan for the adult plant
Check the seed description for mature size, not just the appearance of a seedling. A plant needs room for its canopy and roots. Filling every available opening is not always the right choice: neighboring plants can compete for space as they grow.
Further reading: UF/IFAS Extension · Growing lettuce in small hydroponic systems
Treat fruit as the next project
Longer-lived fruiting crops can be more demanding in small systems. Before choosing one, confirm that its variety, mature size, support needs and growing guidance match the equipment. A fruit-filled product image is not evidence of the harvest you will get.
Further reading: UF/IFAS Extension · Building a floating hydroponic garden
Sources & further reading
Original GrowGrid explanations informed by university extension guidance. The linked guides describe different growing systems; they do not endorse GrowGrid products.
