I think it is just about giving it a go! Just get things that you buy all the time from the shops and stick them in the ground! If you follow your common sense you'll end up with something to show for it. If you encounter any problems this forum is really good and there is always stuff on other sites.
I only started a couple of years ago and in my first year i only did peppers, tomatoes, peas and cucumber- i ended up with like 6 tomatoes, 4 peppers, a few peas and 1 cucumber after alot of effort but i loved every second since then I have got better and have got a range of stuff this year, some of which i am already harvesting.
You'll be fine, just go for it! good luck