I recommend python, cuz its ez to learn and u can do a lot with this language.
Java is also a great choice. its cross platform and with eclipse and netbeans u have 2 very good IDEs, that can help u to learn Java at the beginning.
With Java and Python u can build your own bot from scratch.
There is a great IRC API called “Pircbot” and the modern version, based on Pircbot and fork by some1, called “PircbotX”.
Both on GitHub. in my opinion worth a look.