For an experienced grower, high quality genetics are a very sound investment. Buying seeds from reputable dispensaries can help to ensure that you receive high quality genetics, but this can also come at considerable expense. Because there is an increased liklihood of making mistakes as a beginner, you might consider starting with bagseed. They're essentially free, and you know ahead of time what the final product should be like. Keep in mind that if there are seeds in your baggy and you choose to grow them, the end result should be better than what you originally had.
If you have invested a lot of money in your growing equipment and a lot of time in educating yourself, you may find it worthwhile to spring for more expensive high quality seeds. However, if you just want to throw some seeds in a pot with some soil and let it sit on your back porch, you may as well run with bagseed first, just to get an idea of the growth cycle of the plant while you continue to educate yourself and invest in quality equipment.
So next time you feel burned for finding seeds in your bag, turn that frown upside down and try your hand at germinating them. You may find that those seeds will pay off quite handsomely!