Welcome! You're in the right place. You need to read, read,read. Check out the wiki here, and the sticky threads at the top of each forum heading. Use the search button for any questions you have, and don't be afraid to post the questions you can't find answers to.
If possible, you should find a local brew club, and see if they have an upcoming brewday, or if one of them would let you help out on their next brewday. Hands on is the best way to learn.
As for your original questions, most homebrew batches are 5 gallons, so you will probably need more grain. Usually you will choose a recipe that matches your tastes, then shop for the needed ingredients. Check out the recipe index above for what is needed for any particular style.