I want to learn the more advanced features of klipper but I find myself with some keybinding conflicts and such.

Before everything Cltr-Alt is assigned to kbd to change regionalization layout. I dont want to change that

I want klipper to do the following:
On Gmail I want to copy the recipient, subject and body, and then let me choose what buffer I need to use.

First I modified the shortcuts so I can use them, choosing Cltr-Meta-.... instead of Cltr-Alt.
Then it worked, I did Ctlr-Meta-Down will show me the history.

However when I put Ctrl-V... it paste me STILL my last selection regardless of which showed as Current.

I wonder if there is a way to do something like Ctrl,1-2-3 to do secuesial paste. Is this possible?

The behaviour of Ctrl + V will be controlled by the application in question - although Klipper as the clipboard manager could simply "replay" the contents of the clipboard. As far as I can tell though, this is not possible at the moment.