I must confess, the only things I ever grow my own transplants for are the cole crops, which my local nursery never brings out early enough. It can be a pain, and for most things is not usually worth it. The trick is knowing which ones to buy transplants for and which ones to direct seed. Legumes, like peas and beans, gourds, like melons, squash, zucchini, and cucumbers, and corn will do better if direct seeded in your garden. Strawberries will take 3 years to produce fruit if you start them from seed; you should always buy plants. Likewise, everything in the nightshade family, including tomatoes, peppers, and eggplant, take far too long to germinate and grow to decent transplant size; I always buy plants. Most annual herbs like dill and basil can be started either way with little ill effect. Your growing season is shorter than mine; you'd probably be better off getting nursery plants for them as well.
Any aromatic herb will help keep the insect predators away, so just spread them here and there throughout your garden. Basil and oregano are especially good at this. There is only one combination you should avoid: don't put dill too close to your tomatoes. Dill attracts the tomato hornworm. Also, be careful where you plant anything in the mint family as most of them are very invasive and have a tendency to take over. I love the smell when I hit my peppermint patch with the weed eater, but I wouldn't want it in my garden. Cuttings yes, as a mulch, to keep the bugs down, but the live plant is not welcome. The only non-invasive mint I know of is basil. Oregano is fairly safe, too. It creeps and spreads slowly, but is easier to control than peppermint, spearmint, or catnip.
If you want more produce from your garden in less space with less work, you should look into intensive gardening. Two books have really helped me. Square Foot Gardening, by Mel Bartholomew, and Cubed Foot Gardening by Christopher O. Bird. I use a combination of their two methods, plus a few tricks of my own. Mel tells you how to create cheap, effective, strong, long lasting trellises for all your vine crops, and does an excellent job of explaining how different crops grow and how to plan your garden to make the most of your space and time. However, the soil mixture he wants you to buy can get outlandishly expensive very quickly unless you are planning a very small garden. Also, some of his plant spacings are simply too close together if you use anything but his soil mixture. Chris's soil mixture is much more reasonably priced and readily available, and his plant spacings are better. He also goes into more detail on his own methods of growing some specific crops that I otherwise might never have tried.
Shifting from single row gardening to raised bed intensive gardening will seem weird, especially if you've been doing it the old way a long time, but you'll never regret it. It takes a little money and a little time and effort to set it up, but once it is there, you never have to redo it and keeping up with your garden during the growing season becomes almost laughably easy. With my old single row garden, I could never keep up with it. The weeds took over, my corn was tiny, I'd barely get enough beans to make a meal, and I'd end up mowing the whole thing down out of disgust halfway through the summer. Now I eat fresh all season, put up enough to last the winter, and still have plenty to give away. And it's practically work free. A lot of days all I do is walk out there, give it a little water, pick whatever is ripe, and go back in.