Is performance really important when choosing a language for a trading bot? The C programming language outperforms interpreted languages such as Python or Ruby, but when it comes down to programming productivity, it is much easier/faster to write a Python program than a C program.

Considering that I want to write a trading bot, what would be the most appropriate language? If I use C, will I see a noticeable performance difference, or would the latency from HTTP calls make my decision time irrelevant?
The latency for gathering information and executing decisions will swamp the performance difference between languages. That assumes you don't write horribly awful code, but you can do that in any language. You should use whatever language you are most proficient in or whichever one you find easiest for the task.