For confidence, getting in front of spectators with your magic repeatedly will help you build it. If you can't deal with strangers on the street right now, find another way to start breaching your comfort zone as far as who you're performing for, and do it often. Repeated exposure to the stress of dealing with crowds will desensitize you with time. Also, framing it properly in your mind is important. Remember, the body does the same things physiologically when it's under stress or mounting up courage. When you experience your bodily anxiety response (breath quickening, adrenaline pumping, etc.), remind yourself that your body is gearing up for courage. By mind-framing the bodily response as courage instead of stress, you can use it to your advantage instead of letting it paralyze you.
As for closers, you're going to want to use something called a "reputation maker." This doesn't have to be a big illusion or trick, but it should definitely be among your best. Classic magic is also good to use here. Routines I use now that I think are strong enough to close with include my handling of "Serial Biller" by Rich Ferguson (destroyed and restored dollar with serial number verification at multiple points throughout), "A Single Needle" by Wayne Houchin, and my own cups and balls routine (affectionately deemed "Redbeard The Pink's Circus of Crap"). None of these are particularly large scale, but they play well from small to medium-large audiences at least, and they involve spectator participation in unique ways.