I am not sure if it is correct, but i often think that giving should be without expecting something back
Absolutely, otherwise it becomes "exchanging" and not "giving".
I am not sure if this will be of any help to you Satanus but I will share with you some things which I have noticed:
When I was very young I would give to others at the nudging of adults. My reward was knowing that I was following adult instructions.
When I grew up (teens and early twenties) and gave to others without prompting, there was an element of personal ego boosting involved.
Now I give as an automated reaction simply because I believe that is is what must be done - part of my civic duty.
If because of your JW past you have a bad taste in your mouth regarding ulterior motives then I suggest you simply make (a measure of) giving a habit and you will find that, over time, ulterior motives or ego play less of a role.