It is definitely easier to say that Chris was not prepared for the wild and to cite examples of that, but I'll start with how he WAS prepared...
First of all, Chris did carry books on local vegetation so that he would know what to eat and what not to eat--as you know though, this book did not save him from his demise--in fact, one may be able to argue that it contributed to it.
Secondly, he did have a gun with him and was therefore able to shoot small game and some larger game as well.
Thirdly, he was mentally prepared. This was what he wanted to do more than anything in the world, and he was prepared to do whatever he needed to survive.
As far as his lack of preparedness goes, the list could be much longer!
First, he had no up-to-date maps--if he did, he would've realized that help and possible shelter were mere miles away.
Second, he did not have enough food--a bag of rice is just not going to work!
Third, he did not know enough about the terrain, the river and the surrounding area to know how to live and sustain life! If he had done his research, he would've known about the swell of the river, the ranger station and the cabins nearby.