You do want to be careful not to overpower a recipe with too much or too many spices. The University of Delaware has an excellent description on the intensity of herbs and spices:
Strong or dominant flavors – Includes bay leaf, cardamom, curry (actually a blend of spices), ginger, pepper, mustard, rosemary, sage
Medium flavors – Use in moderate amounts (1 to 2 teaspoons for 6 servings) Includes basil, celery seeds and leaves, cumin, dill, fennel, French tarragon, garlic, marjoram, mint, oregano, savory, thyme, turmeric
Delicate flavors – Includes burnet, chervil, chives, parsley. May be used in large quantities and combined with most other herbs and spices.
Sweet flavor (combined in sweet dishes may let you reduce sugar) – Includes cinnamon, cloves, allspice, ginger, cardamom, anise, fennel, mint.
Savory flavor – Oregano, tarragon, chives, dill
Peppery flavor – Red pepper, mustard, black pepper, paprika. Use with care since their flavors stand out (approximately 1 teaspoon for 6 servings)