When buying bait the golden rule is fresher is always better. There are a bunch of different kinds of baits out there but to start i would say just buy some shrimp. Shrimp is cheap and pretty much everything will eat it, but i would say if you go to a bait store ask for the fresh shrimp. The frozen shrimp loses a lot of its smell and is generally just worse, but will work if that is the only option. Some people do this different but i have had more succes with taking the shell off of the shrimp then putting it on the hook. Another good thing to do is when you do catch a fish off the beach is use this for cut bait. Generally the bloodier the fish the better, for this you should try to target bluefish, mullet, whiting, and shad but make sure to follow all the regulations and laws as this still counts as keeping the fish.