Honestly, I think the Tantus Neo would great for a beginner. The tip makes insertion easy, the girth isn't overwhelming, the neck is fantastic, and the base is super comfortable.
I agree with Trysexual about the Mood naughty plugs, they're not too big, the neck is slim, and the base is made to sit comfortably. Plus, they're less expensive, so you can figure out what works for you without breaking the bank.
*I've worn both for upwards of 2 hours with no discomfort.