I want to buy some xrp and hold them offline I want to buy some ripples (xrp) and hold them offline ( I want to keep the secret key with myself rather than trusting some hosted websites). Are there any steps to do this? Is ripple trade account mandatory to hold xrp? Can I simply buy xrp in cryptsy.com using btc and transfer them to an address managed offline in my computer?
Download "ripple-paper-wallet" https://github.com/OctillionSA/ripple-paper-wallet
Open index.html (HTML/javascript) in a browser (on a PC without Internet, better a fresh new OS).
Write down or Print out your paper wallet.
The public key starts with "r" is your Ripple address.
The private key starts with "s" is your "Secret", keep it safe! You can also use it in case you want to migrate your wallet to online GateHub or to any other wallets. (but it won't be a cold storage after that)
Activate this wallet by sending small amount 20XRP (or more) to the address. (You can activate it here: https://bithomp.com/activation/) 
Make sure you address is visible in the explorer: (https://bithomp.com/explorer/). 
You can "erase" PC which you used, or just turn it off together with the printer to clean memory.


Congrats: Now you can send big amounts to this address.

P.S: You can also buy a Hard Wallet. like "Ledger wallet" for example. - also a secure way to keep your XRP.