You should read the stickies.. If you put rocks in make sure that they're not just from outside and if they are they should be boiled. As for plants you can put real ones in, or silk plants, other types will tear the his fins. As for food you should feed him betta food, such as Hikari betta pellets.
Some fish don't have as nice fins as anothers, keeping his water clean and putting up a mirror for 5, 10 minutes every other day in front of his tank so he can flare usually helps though. Do his fins look all raggy, or just clamped together?