Try adding the following styles to your template's CSS, which should do what you're looking for:
div.social-login {
font-size: 18px;
margin: 10px 0;
}That increases the font-size and adds 10px of space above and below the row of social buttons.
.social-login .pull-left {
margin-right: 10px;
}That will add space between each of the elements in the login row.
I hope that helps, but if you have any questions, just let me know!
Thanks,
Alex