If I already own a coin I want the trader to trade (like Dogecoin), do I need to sell it first?

No, you don’t need to sell it. However, if you add Dogecoin to your active trading list in GoBabyTrade, the system will treat your current holding as a single lot at the current market price—not your original cost basis. This isn't a concern if you simply want to use the trader to accumulate more and not sell.

However, if your goal is active profit-taking, we recommend starting from cash (USD or USDC) and letting the trader build new positions from scratch. This allows the trader to use proper Money-Management / Risk-Management to allocate the funds so it can buy at different price points and respond to market movements strategically.