There are not many places to find petanque equipment. Currently the best places to look are Pétanque America and Decathalon. It's important to understand the difference between "leisure" boules and "competition" boules.
Choosing Petanque Boules
When you decide to buy your own set of petanque boules, it is important you choose the proper size and weight for your particular needs. You can find online guides by OBUT by Playaboule and by All About Petanque. Before you make an investment, it's a good idea to consult one of the experienced players to be sure you are making a good choice. Players usually have extras sets of boules of various sizes and weights that you can borrow to see what works for you.
The general rules of petanque are really pretty simple. There are several "technical" rules that matter in serious competitions, but beginning players don't need to be overwhelmed trying to learn them. You can get started by just reading the Basic Rules of petanque. You can find all the official rules at the USA Federation of Petanque. In general, new players can just get in a game and learn as they go. Other players will be happy to explain.