Looking for advice on learning GP-Pari

[JmsNxn]

Several years ago Stephen Wolfram offered to give me a copy of Mathematica. Unfortunately the gift was only for one year. A few times I reached out to Wolfram Research to renew Mathematica. Wolfram asked me to write Mathematica software for Wolfram Functions supporting tetration, but I have to either buy or beg for Mathematica. So time to move on to a public domain mathematical programming language. 

What resources do folks recommend for learning GP-Pari? I looked on Amazon and there is only a couple of expensive books on using the programming language. Is it all just online resources? 
Thanks,
Daniel

So lucky for me I come from a strong C programming background; therein Pari-gp was only a slight difference in syntax. So most of the time I'd be asking "how do you run this function that I know how to do in C" and just converting the code. I found that Pari gp has great, and I mean great online documentation. There's the official phd level paper breaking down everything, and plus a vast resource of helpful explanations of every built in protocol. Pari-gp, despite looking very user-unfriendly is actually very user friendly. But it's not like object oriented programming languages, which I believe Mathematica's scripting would fall under more. This is much more akin to C.

I'd suggest writing simple math programs you know how to do. Like, how can we write a program to iterate the exponential?
Like, write a quick function that satisfies \(\exp^{\circ n}(z)\). And familiarize yourself with the language.

Can I implement Newton's root finding algorithm? Or can I do it for weird functions? Try doing that, simple things.

Honestly, I've found Pari-gp to be one of the most natural languages. But that's also because for me programming in Java or Python is a nightmare, where as C is fucking awesome. Honestly, the beauty of pari is the online resources. Use them. They're fantastic!

I'm not the best at Pari, but I know how to use it for what I want. If you ever get stuck just pm me and I'm happy to help

Regards, James