Rocket league trading ps4?

My question would be as follows: I have now bought 1000 credits to trade, but I don't have such good items yet. Could I spend these 1000 credits in the shop and still trade with these items? Or do you have to keep at least 500 credits in your account to trade?

You only have to buy 500 at least once - you don't have to have them all the time

You must have bought at least 500 credits the first time, then you can always trade, you don't have to pay anything!

You can spend the 1000 credits in the shop, but you can't trade items from the shop!