What do these two seal stamps and these three characters on my Chinese painting mean?
The characters written in black ink is the first name of the painter (寿民 Shoumin). If you Google it, there is a painter named 边寿民(Bian Shoumin) in Chinese Qing Dynasty. 

Here is a link to Wikipedia https://en.wikipedia.org/wiki/Bian_Shoumin

You can also Google the word “边寿民” by image to see his other paintings.
If this painting is not counterfeit, It would worth around 500,000 in Chinese Yuan ($80,000).

The clearer seal is “志紋墨寶”. In my understanding, 志紋is also a person’s first name. 墨 means ink, 寶 means treasure. Therefore, “志紋墨寶” means 志紋’s treasured painting.