How to set cursor to after last character in vim?

What you want is to use is the a command instead of the i command to enter insert mode. Or if you want to jump to the end of the line and start insert mode, use A. Note that I will jump to the beginning of the line and enter insert mode.

You can also put set ve+=onemore into your .vimrc; that'll let you put the cursor onto the "empty" space at the end of every line.  Note that $ will still put you on the last character; you'll need to use something like $l (lowercase "L"),  /$Enter or  99| (vertical bar).