Baby steps will eventually get you there.
1. parktool.com is your friend. They have step-by-step instructions for tuning your bike. When their directions leave you befuddled, ask here in the Bike Mechanics forum where some professional and skilled hobby mechanics hang out and, I promise, they'll have answers.
2. Don't be too quick to take a screwdriver to your derailleur. Sometimes the limit screws need to be fiddled with but most derailleur adjustments are made with cable tension barrel adjusters. Always try that first.
3. I don't do this anymore but, when I was learning to work on bikes and didn't have any money, I used to cruise the neighborhood on garbage pick up day looking for bicycle discards. I can almost guarantee you'll find a front wheel that way but maybe not a rear.
Oh - and I was serious when I said that the purpose of your first bike is to figure out what you want your second bike to be.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.