If a Rov gave a gift every time he was invited to a simcha, he would go bankrupt. His presence at the simcha is a gift. For the rest of us however, a gift should be given, based on what we can afford. If the people who invited you are not happy with what you can afford, they will not invite you again. Big deal. You’ll save more money. People who care about you will understand (unless you can afford a gift and are merely being a cheapskate, in which case, SHAME on you!).
I had several people who came to my kid’s weddings and gave nothing. In two out of three cases, they could not afford a monetary gift, but they each took non-professional candid pictures of the simchas (very lovely ones, btw), and put them together in an album for me. It meant a great deal to me. One person simply forgot to give, and never realized it. Moichel. If people matter to you, you don’t make an issue of it.