I agree. For now, you don't need a fancy reel. But if you get into it, you will want one later.
The only reason for attaching a leader for practice is so you can see how the very end of your line "turns over." Does it pile up or make a huge arc or lay out nicely? You can attach some colored yarn to the end to be able to see this. For learning purposes, I'd start with something short - buy a 3x seven foot tapered leader. You won't need a tippet for practice unless you're going to be breaking off tangled in the trees or something. A tapered leader as opposed to just tying some mono on the end will "turn over" correctly if you are casting correctly. Again though, attaching leader and tippet is not a necessity for practice.
Your fly will depend on what you're trying to catch. For a 7-weight, you have covered a ton of casting bases in that there aren't too many flies you can't cast (unless you are throwing big streamers for stripers or something).
Although a 7-weight might be considered a little big for bluegill and small bass, you might start there because they are easier to catch. You can just toss a small popping bug (whatever size you think will fit in the mouth of whatever size fish you're catching).
For now, I wouldn't worry about a "dropper" fly (a second fly trailing the first) as this easily tangles with beginners (and some veterans like me!). Another route is to strip and twitch a streamer like a wooly bugger, a super bugger (my favorite), a Clouser minnow, or a muddler minnow.
If you want to tackle some trout, we can add some nymphs and a strike indicator to your arsenal, but I'd start with some of the easier quarry until you get proficient.
I will add an addendum that some folks may disagree with. Fly casting and fishing are not that hard if you learn correctly and put in some practice. I decided to learn on my own, and I picked up some bad habits that took years to correct. If you really want to save time and money, go spend some time and a little bit of money. Take a beginner's class at one of your local fly shops, and get a guide who will teach you the right way to do things.
I hired a guide after five years of self-taught fumbling. I learned more in those three hours than in all those five years before. Good luck.
