It's always great to have a great offense in volleyball, but you need to have a just as good defense as well. You need to have a great defense just incase the other team has a good offense or they have a really good defense and can receive all your balls.
No one likes playing defense, but everyone will have to play it one time or another. Most people don't like playing defense because they aren't consentient on their passing. To get you more confident, you should practice a lot on passing, so you won't mind being on defense and it'll feel good to be able to pass the other team's spikes up to the setter. There really isn't one volleyball defense drill that's better than the other, but I'll just name a couple things you may want to try.
Volleyball Defense Drills:
- Do a lot of passing up to the setter with all different hits over the net. For example, pass up hits, free balls, sets, serves, etc.
- Do “wall its” to help build your legs up so you can stay low longer
- Just practice staying in your down and ready position for a minute
- Do squats to build up your legs
- Practice diving the proper way so you won't get injured
Also see volleyball training aids for more details.