The overall layout looks good but you've done a major problem with the colors.
The text isn't readable so try to change the colors as shown in the style guide. It will make the card look much better.
Also the very first heading "Join our Commmunity" should have a larger font-size. You should write this inside of an h2 element because this is an important heading.
To make the card look like a "card" use box-shadow property. Here is what I used:
box-shadaow: 1px 3px 15px rgba(0, 0, 0, 0.2);