w00t, congrats. It's a long but rewarding journey.
1. I use half dollar coins. They're a good size for most. (one size fits all

). They're visual, and they palm nice. Just go to a bank and pick up some, if you don't already have them.
2. soft coins are coins that are smooth, so they don't "talk" or make noise when clinked together. They're nice for routines when you're finger palming two coins, 'cause you don't want them to talk.
3. Bobo's isn't really the best start for a beginner. It's kind of outdated, and doesn't go into a lot of detail. I would recommend David Roth's "Expert Coin Magic Made Easy". It's a 3 volume set for about $45, and it teaches coin magic
really well. The first DVD teaches essential palms and other moves, as well as some routines. The second DVD is slightly more advanced, and it teaches some great moves and routines. The third DVD is the expert level, and is the stuff that David Roth is famous for.
The set is fantastic. It will take you from beginner to (almost) pro, if you follow everything carefully. Dai Vernon called David Roth "the greatest coin magician in the world." It makes sense.
4. Coins get great reactions. I've performed card effects and coins effects for people, and when they see me again, I'm still asked to do my one coin routine, or coins across! Coins are really great to do magic with, and people love them. In a formal setting, I use my own half dollars. If it's a casual street performance, or for friends, I just borrow some quarters and rock it.
After you get the basics down, you should get Jay Sankey's "Revolutionary Coin Magic". It teaches lots of great routines, including "Mr. Clean Coins Across" which I perform multiple times a day. Probably my favorite routine in all of coin magic. You borrow three coins, and cleanly make them travel from hand to hand. Awesome. David Roth's book is great, too. Michael Ammar has some good coin stuff.
Make sure you practice well, and enjoy performing coins!
As soon as you get a good routine down- go out and perform it. It's rewarding, and will keep you going.