Do you all start with seeds or plants? Also were do you get your seeds?
The choice between seeds and plants is not too tough once you understand a few basic facts, such as how hard or easy, and how expensive or inexpensive it is to do one or the other. Also, how long it takes to grow to seedling size and the value of the plant at maturity have a bearing. I'll give you some examples to illustrate:
As a general rule the smaller the seed, the harder it is to grow in the virgin soil, and therefore the greater the argument for using seedlings. Carrot seeds are very small (19,000 per ounce), and so one would think they would need to be transplanted from seedlings. The problem is that ROOT CROPS, like carrots and parsnips, are difficult and time-consuming to transplant, and they do not do well, even after transplanting. Their roots will not be straight and long, but will be bent and misshaped.
Individual carrots also have a very low value per plant at maturity, and so don't justify the time and/or expense of transplanting. The same is true of radishes, etc.
Tomatoes, peppers, eggplant, etc. have small seeds, plus they take a long time (7-8 weeks+) to reach a size that does well in the garden, AND they all have HIGH value. Therefore, these are almost always recommended for transplanting into the garden as robust, healthy seedlings.
A few examples of plants between those extremes include :
1) Cabbage, lettuce, etc. have small seeds, grow quickly, and have low value per plant, yet they are often transplanted because transplants are healthier, grow better and faster, and because thinning is such a hassle.
2) Peas (hardy) and beans (frost intolerant) have large seeds and grow fast in the garden, yet are sometimes transplanted to get an early start to maturity in the garden.
3) Squash, cucumbers, and melons (frost intolerant) have large seeds and grow fast in the garden, but are often transplanted to avoid losses from garden pests and to extend the season by putting healthy seedlings into the soil about the same time you could plant seeds.
You can buy seeds from dozens of reliable sources in America. For small gardens look at the seed packets in your local stores. For more serious buying, go online and order from the large seed companies, such as Burpee, Park, Gurney, Harris, etc., etc.
I don't recommend you get seeds from a friend, or from an internet seed-sharing source. The reasons include the fact that un-certified seed can introduce disease into your garden that can be devastating, and it may not give you the results you were expecting because it got cross-pollinated or wasn't exactly as represented.