Purchase process

Seriously thinking about buying some soon. So far I learned I do not want to buy through and exchange. So I was going to buy through Tor browser via robosats using wallet of satoshi w/ amazon gift cards likely (not sure if this would work for higher $ amounts/don’t want to use my bank info). From there mix in Sparrow using a Mac. Thought about simply using BTCcore as a node but not sure where that fits in this process. Then from sparrow to cold card. My questions are the following:

Likely not going to be making many transactions other than buying and holding, do I need a designated computer? Or a node even?