There is a basic Kanto version, an expansion theme Johto with new capturable Pokémon. Together, you can capture all first 251 Pokémon. Both games use the same assets. There are also versions of Hoenn and Kalos available.
It depends on how pretty you want the game to be. You can print everything in black-white and if you don't laminate the cards it will only cost you like 10 bucks. However, if you print everything in colour, laminate the cards and buy additional assets such as counters and pawns, it can cost much more. It will result in a beautiful boardgame though. For information on how to print you can always check the printing section on the How to Play page.
There is no single best tactic. There are many viable tactics, but every one of them still depend partially on luck, so nothing is guaranteed to always work.
Every battle is a battle, but not every battle is a duel. A duel is when you land on a duel tile and battle one of your opponents using one Pokémon. Every other kind of battling is not a duel.