Good ideas for Inca?

[Reverend Belial]

I know I'm going to need colonisation ideas one way or another, but should I get expansion or exploration? And what should I get before/after that? Any tips would be appreciated.

[Kagemin]

I started with Exploration. The extra colonist helps, and Conquistadors allow you to get a better overview of the continent and see all the places the Europeans settle.
A point can be made for getting Expansion as well, but personally I don't think it's really worth it in this case. Depends a bit on what you're trying to achieve though, I mostly focussed on the Sun God achievment and didn't do much outside of south America.

I went with defensive as my first military idea, cause it gives you the biggest boost the fastest, and in the early wars against Europeans you need everything you can get by then.

And my first admin idea was religious, Inti has a terrible conversion rate without it. You can probably get by with Humanism and tolerating too, but I just don't like Humanism. Plus I played as the Theocracy down there and found it more fitting. :p

After that it depends a bit on your situation. Maritime can be great, you'll probably make a ton of money from pirating and/or trade that flows from the Americas to Europe. If you have enough of a grasp in other regions (went into south east Asia for example) Trade might fulfil that role better though.
Military is mostly a matter of personal preferences, so whatever you like should be fine.

[Banana Tiger]

I can recommend you watching Armuba's EU4 lets plays. Here is El Dorado Incan series started as Cusco (in progress, already 23 episodes):
https://www.youtube.com/watch?v=89HeM_cUAcI&list=PLH-huzMEgGWDB6lzIUASvrZEV20bby5Vs

[Bole]

Choosing ideas is situational but good choices for Inca are based around colonization and strong military you need to fight westerers. Innovative also gives huge boost, ended with 155k gold.

http://steamcommunity.com/sharedfiles/filedetails/?id=404196734