as long as you don't use a credit card with your name on it you will be safe. purchasing a vanilla card from Walmart is probably the safest online shopping method because if you do stumble onto something you shouldn't you won't be easily traced because many malicious site owners set up keyloggers that fish for credit card info, names etc at the exit node of the TOR browser.
Because of the deep web where you can buy guns, yellow cake plutonium and drugs steal identities...etc these keyloggers are set up by the cartels to track you right to your home address. the safest way to use it is NEVER use anything that is attached to who you really are.
also if you do plan on using TOR please watch all videos of its vulnerability before you do decide to use it. when a website asks you to install something like flash player because TOR does not use it your operating system will automatically switch off of TOR to install whatever tools needed to show the full page, that is when the keyloggers try and gather as much info on you as possible this also includes cookies most sites demand you have cookies turned on especially places like Facebook Twitter and most social media
Be very careful before using this.