Widget customization for my theme, help please!

I’ve got the widget on my site over here:

In addition to the “your best email” code from this page:
http://wordpress.org/support/topic/plugin-mailchimp-list-subscribe-form-request-add-placeholder-text-for-mailchimp-widget?replies=8

I added this CSS:

#mc_signup_form .mc_var_label {
display: none;
}

#mc_signup_form .mc_input {
float: left;
min-width: 0px !important;
width: 100%;
color: black
}

#mc_signup {
width:200px;
}
.mc_merge_var {
overflow: visible
}

What I’d like is for the “your best email” placeholder text to work and for the SUBMIT to be on the same line (perhaps a bit smaller). I’d like to lose all the extra space below the signup.

Please help mailchimp! You rock!