As a first anal toy, I DO NOT recommend the Tantus Acute. I've used it lots of times and I'm an experienced anal user. While the Acute is a quality dildo that's probably wonderful for vaginal stimulation, it's quite uncomfortable for anal stimulation, especially for a beginner. The reason is that the head of the Acute is way too bold and pronounced. It makes insertion very difficult and uncomfortable (unless you're already warmed up). Also, the ridges along the shaft make thrusting a little uncomfortable. I found that my butt was a little irritated after thrusting.
Instead, for a beginner toy, I highly recommend the Tantus Silk medium. It's completely smooth without a bold head, and it has a large base perfect for holding on to. They're both a comparable length, however the Silk medium is 1.1 inches in diameter while the Acute is 1.25 inches in diameter. For a beginner, smaller would be better.