What's the easiest language to learn?

I'm planning on learning a few languages, and I want to start with something easy. Thanks for reading.

Learn Esperanto solidly for three months and you will be fluent, once you've done that every other language will come a lot easier. If you're already at least bilingual don't waste any time with this step, but based on your OP you're looking for your first secondary language so it should definitely be Esperanto. This isn't the only utility of Esperanto, but if you are serious about learning languages then this factor alone should make you want to take up Esperanto immediately.