going between insert and normal modes (i and esc),
undoing (u from normal mode),
and saving (:w and :wq).
Don't try to do it all at first, just get comfortable with the essentials. You can even just stay in insert mode (the only mode in most editors) at first.
Keep a vim basics cheat sheet handy for a couple weeks as you're building in muscle memory, then slowly work in more advanced techniques and combinations.
It doesn't take long before you start having a lot of fun just manipulating text.
Depends how much time you spend in a text editor. If it is just for a few config edits and stuff, honestly there is little reason to learn. The real benefit is if you spend a lot of time editing text due to the time saved using more powerful commands. There is the additional benefit that vi/vim is installed on practically any Linux box, so you will almost always have a familiar editor to hand in an unfamiliar environment.
I became a fan after I got used to nice color schemes, buffers/tabs, horizontal/vertical splitting, file browsing with NERDTree and highlighting changes with GITGutter.
You ask for tips? Add VIM commands you use regularly (like paste mode toggle for example) to a keyboard shortcut (like leader key + p) in your .vimrc settings file. It increases working speed.
Also add some plugins, they are fun and add useful functions from other editors like Sublime (ctrl-p, vim-multiple-cursors).
There are plenty of cheat sheets online. The main thing is understanding that there are different modes, knowing what they do, and how to switch between them and issue commands.