I just got started and just have a blockchain.info wallet. Do I need to have different wallets, or is just the one sufficient?
You should have an Offline wallet, one that holds your "savings" and the online wallet is sortof your "chequing" wallet.
Online wallets are infamous for getting hacked and people losing thier money, you can't "hack" something that is offline that one does not have access to.
Try the standard bitcoin client (takes up alot of HDD space and has to sync) or try Armory (safest) or Multibit (high compatability)
One wallet is sufficient for functionality, but thats the bare minimum, you should definitly backup your wallet and have a seperate offline one