Elgg templates works similar to WordPress, so once you wrap your head around API and plugin strjcture, you can manage. Main difference is that WordPress dumps an entire page into a single file and each plugin tends to reinvent the wheel over and over. Elgg uses views, which render HTML, so in theory you can use plain HTML and only use bits of PHP, where you want server data output. But to be good at it, you might need and should learn some PHP. It's not rocket science.