I wouldn't say that since he is asking he shouldnt try it, because everyone has to start somewhere when trying new tricks. A good rule of thumb, is if you can do 360s consistently then you can try flips. I personally found that when I started to do tame dogs they were just as difficult as 360s.
Flips are usually just a matter of commitment. If your not fully committed to throwing the flip around, then don't try them. If your trying flips in pow, do a wildcat. It is very difficult to do a tame dog in pow, because you usually can't get enough compression in your nollie to throw you around.
Also, the jump also influence the flip. For back flips or wildcats, you want either a really poppy jump or a nice med-big jump. For tamedogs its easier to do them off drops.