Let's see, trustworthy place to buy seeds. I mail ordered most of mine. The ones I bought at my local garden center were usually from Burpee, an old, well established company. They stand by their product if there is a mix-up. Johnny's is another very good one. See if you can get their paper catalog, there is a great deal of how to information for each selection. I found it very helpful. They too stand behind their products.
Read the compost sticky above, lots of information there. You are correct, sewage sludge is gross, not matter what those selling it say. Topsoil on the other hand, can be an option. When we did our garden, we got a dump truck load of it, something like 13 cubic yards. Part of the yard was extremely low, we had a frozen pond there in the winter, so it took a lot of soil to bring it up, and then make it into raised beds. That was lots of moving of soil, as it got dumped at the end of the driveway, out front of course.
See if your library has a subscription to Organic Gardening magazine. You could borrow back issues and if you like it, get a subscription of your own. They also have a website, but I always preferred to sit with the magazine, so I never explored it.
Find out if your county extension service offers any educational programs for novice gardeners.
Remember that learning takes time. You will have both successes and failures, that's perfectly normal.
Ask lots of questions here, gardeners love to share!!