Inks also vary more than you would expect! I don't have a vast collection of inks, because I want a very specific thing: water proof (or at least water resistant, so a drop of tea won't wipe out what I've written), and I like dark green and black colors. My general go-tos are:

Noodlers Heart of Darkness (black)

I feel this is the most reliable ink. If a pen is being a bit hard to start, I use this ink.

Noodlers Zhivago (dark green)

One of my top favorites. It's just a lovely rich almost-black green and I like it.

Noodlers El Lawrence (dark olive green)

My other top favorite. Dark green but a bit more olive than Zhivago.

Noodlers 54th Massachussets

I don't really like the blue color, so don't use it much, but wanted to mention that this is a very wet ink. If a pen is a bit dry, this ink will flow. Don't use it in a pen that is already on the wet side! (I should try it in my Sailor.)