well John, one thing I would recommend is to try sleeping outdoors overnight in a borrowed summer sleeping bag if possible, just so you have an idea of what you are comfortable at. In general, an inexpensive summer sleeping bag inside a tent, along with a fleece and some long tights/underwear/plain camping outdoor long pants, will cover summer camping.

I take it from your question that you havent camped before, but most people will be comfortable in a tent using a summer bag--of which I know there are tons of at diff prices, diff temp ratings, diff packed sizes etc etc.
There is no downside to you visiting a number of good, established outdoor stores, depending on what country you are in, so at least you can see diff equipment and ask some questions. A large, well established store will have knowledgeable stafff who most likely have real life experience with camping situations, and at the least you can start to get an idea of what range of prices etc are available.
A good campmat is also important for warmth and comfort, although depending on your age, you may not care too much about that, but again, like sleeping bags, there is a big range of prices for campmats, and a large store will have examples hanging out of package that you can take down and lie on to try out.