You do not need many tools to harvest cut flowers, but the ones you have should be sharp and clean.
Bypass pruners (like Felco) for woody stems and thick dahlia stems. Floral snips or sharp scissors for softer stems. A harvesting knife works for high-volume cutting. The key: clean, sharp blades that make smooth cuts. Crushing the stem restricts water uptake.
Tall, clean buckets for collecting stems in the garden. Restaurant supply stores sell inexpensive tall buckets that work perfectly. Have several so you can separate flowers that need different conditioning (like daffodils).
Rubber bands or twine for bundling stems by variety. A garden cart or wagon for transporting full buckets. Bleach for sanitizing buckets between uses—bacteria in dirty water is the number-one killer of cut flower vase life.
Johnny's Selected Seeds carries a good selection of harvesting tools specifically for cut flowers.