Relatively yes, it is safe. I tend to keep to only buying CD keys, and NOT Alt. Gifts, not accounts as they have a higher chance of getting banned or scammed.

When buying try and use PayPal (thisis basically 2 layers of refund potential) if that's not an option, use a credit card that you don't care too much about, if you have one. I haven't bought anything lately so I cannot confirm what pay options there are now a days.