How do I become more grateful?

First of all, drop this "more". More devotion, more gratitude, more joy, more happiness; we need to drop this "I want more and more".
First you are thinking, "I want more money, more joy, more happiness and more pleasure". Then you shifted your tendency to wanting more peace, more knowledge, more of this and more of that.
As long as you are in the run for more, you are not going to settle. Unless you settle, there is neither peace nor grace. Got it.
So somewhere you should take this whole ‘I want more’ thing and dump it and say ‘okay, that is it!

It is said in the Bhagavad Gita, ‘Yadrccha-labha-santusto Dvandvatito Vimatsarah.’
Whatever is coming to you, you should have some level of contentment and with contentment comes gratitude. If you are discontent, how can you be grateful?
If you are grumbling, you can’t be grateful, and if you are not grateful, how can there be grace? Do you see what I am saying? It all fits one into another.
So now, don’t ask me how can one be more grateful? Just stop complaining!
Know that this whole life is like a dream. It is all going to end and everything is going to finish one day. This very awareness will bring a shift in you.
‘This story is going to end someday and the curtains are going to fall’, knowing this, suddenly a shift happens from the run to having more to contentment. It will come to that.