You may use the English wordpress, while will make your admin panel work as LTR
But in this case, you have to fix the tinymce editor so that when you write a new Arabic post, the text area will be RTL
Here’s how you do it:
1- Go to wp-includes/js/tinymce/themes/advanced/skins/wp_theme/
2- Open content.css file
3- Look for the line which has this: /* WordPress styles */
Under it, you’ll find the body css code. Replace the BODY code ONLY with the following:
body {
font-family: Tahoma, “Times New Roman”, “Bitstream Charter”, Times, serif;
font-size: 11pt;
line-height: 19px;
color: #333;
margin: 10px;
direction:rtl;
text-align:right;
}