I started learning magic when I was very young (maybe 8?) but didn't really get into it until high school (I'm 23 now). I knew a lot of basics, stuff that you get in all the magic kits, but like you, I didn't want to carry around a bunch of weird looking stuff with me. With that in mind, here's my advice. Remember that this is my OPINION and may not all apply to you. Also, I'm not a professional, though I hope that will change in the near future.
Tricks or Technique?:
I would learn tricks. Techniques will come as you go. Magic is no fun if you aren't performing and you can't tell someone "hey, I learned how to force a card, check it out!"
Cards are fantastic. They pack small and can be used to create virtually any emotion you want in your spectators depending on the trick and on your performing style. I've gotten people to freak out, laugh, and get scared in less than 15 minutes with only a deck of cards. Learn a couple of flourishes because, come on, you want to show off just a little. Learn the pass, some forces, and some controls. A good ambitious card routine can force you to learn some great stuff.
Coins. I'm not a fan of coin magic so I'm not the one to talk about it, haha.
I did a lot of magic in high school, and just about everyone there knew who I was. The two tricks that people wanted to see the most (like every time they saw me) were the Self-Tying Shoelace and my metal bending. Check out Banachek's and Morgan Strebler's work on fork bending. It may seem weird to carry around a couple of forks in your pockets, but I was never sorry I did.
Overall, choose tricks that you think are really cool or you won't enjoy performing them.
Practice is super important, but do it right. Don't take shortcuts. Of course practice in front of a mirror, or record yourself and watch it so you don't have to divide your attention between watching yourself and actually doing the thing. Find someone you trust to show things to when they're about 75% ready. I've always used my mom. Then I fine-tune it with the input she gives me.
Be yourself! Don't be afraid to explore different styles, but perform the way it feels natural to you. Enjoy yourself and other people will enjoy it.
Read all you can on WHY magic works. Once you know how people think, you'll know how to fool and impress them. For instance, just taking an extra 5 seconds before turning over the card in the last phase of an Ambitious routine makes a huge difference.
That's my advice, I hope it helps you out. If you're curious what kind of results I get, here's a video of me last night at a talent show here on campus.http://youtu.be/sNPvpd9RtAk